feat(native): inspect offline ELF layout through pwntools (#1037)

* feat(native): inspect offline ELF layout through pwntools

* fix(build): prepare offline ELF verification on clean runners

* fix(native): preserve snapshot acquisition cancellation

* fix(native): handle sectionless ELF and retain decoder diagnostics

* test(native): verify malformed symbol table entry sizes

* fix(native): respect inherited limits and unused segment fields

* fix(native): preserve packed relocations and decoder launch constraints

* fix(native): validate symbol spans and preserve resource failures

* fix(native): preserve diagnostic completeness and memory failures

* fix(native): guard bridge imports against allocation failures

* fix(native): validate relocation symbol and section references

* fix(native): retain diagnostics through compounded cleanup failures

* fix(native): preserve unresolved relocation section references

* fix(native): bound linkage evidence and preserve CPU signal diagnostics

* fix(native): preserve file-size resource failure evidence

* fix(native): retain opaque linkage names and late cancellation output

* test(native): make CPU-limit fixture robust across runners

* fix(native): verify resource failure branches before interpreting exits

* fix(native): validate declared ELF string references

* fix(native): validate section-name table before decoding

* fix(native): enforce canonical ELF name-table escapes

docs/binary-diagnostics.md

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+# Offline binary diagnostics
+
+`inspect_binary_layout` / `inspect-binary-layout` answers what an explicit
+file contains: section/segment layout, original symbols/relocations, static
+linkage names and mitigation indicators. It works without an active Hopper,
+Ghidra or IDA target. CTF is one possible use; crash triage, compatibility and
+ordinary binary inspection use the same modular capability.
+
+## Bring your own engine
+
+Initial real verification covers **Linux x64, ELF64 x86-64 little-endian
+EXEC/DYN/REL**. Provide an absolute Python executable whose environment already
+contains unchanged pwntools 4.15.0, pyelftools 0.33 and Unicorn 2.1.2:
+
+```sh
+REA_PWNTOOLS_PYTHON=/absolute/isolated-env/bin/python \
+  rea inspect-binary-layout ./selected.elf --json
+```
+
+```json
+{
+  "name": "inspect_binary_layout",
+  "arguments": { "path": "/artifacts/selected.elf" }
+}
+```
+
+REA never installs Python, packages or GDB, changes a user init file, launches
+the selected object as a host process, or requests runtime library resolution. The Python process
+uses isolated mode and an owned cache. Exact upstream profiles are recorded in
+[upstream provenance](../third_party/pwntools/README.md).
+
+## Interpreting results
+
+- Artifact path, SHA-256 and size identify original selected bytes. All parsing
+  reads an owned stable snapshot; the original is unchanged.
+- Addresses, offsets, lengths and flags are hexadecimal strings. A linked
+  address is not a runtime address. Runtime load base remains null. A zero
+  EXEC/DYN entry means absent; a relocatable entry is not applicable.
+- Each symbol retains its table and entry index. Its reported value can mean
+  undefined, alignment, absolute value, no address, unknown section index,
+  section offset, TLS offset or linked virtual address. Duplicate names remain
+  separate entries. SHN_XINDEX remains unresolved in the selected upstream
+  representation; its external index table is not silently treated as resolved.
+- Relocatable objects have section-relative relocations and no executable entry
+  claim. Signed REL/RELA relocation addends are decimal strings. Packed RELR
+  tables retain full original bytes and upstream-decoded offsets as derived
+  evidence, with per-offset packed-word locations and implicit addends unknown.
+  Overall relocation inventory completeness remains unknown.
+  A relocatable SHN_UNDEF target or inactive SHT_NULL header remains an explicit
+  unknown with the original reported section index and offset.
+- REL/RELA symbol references retain their original table and entry indices.
+  Positive indices resolve through a validated symbol table; symbol index zero
+  means a zero symbol value without a table lookup, including when no table is
+  linked. Malformed references fail with the affected section and symbol index.
+- Section-name and symbol tables require declared SHT_STRTAB links.
+  SHN_UNDEF explicitly means no section names: display is empty, raw name and
+  location unknown, with the original name offsets retained. Extended section-name
+  indices resolve through section zero and undergo the same validation.
+- Symbol tables require a declared SHT_STRTAB link. Name offsets and terminators
+  must stay inside the declared string table; malformed references fail before
+  unrelated bytes can become names. Dynamic dependencies use DT_STRTAB/DT_STRSZ
+  with a unique file-backed mapping; ambiguous or unbacked mappings are
+  explicitly unsupported.
+- Name display strings use UTF-8 replacement for opaque bytes, including
+  sectionless dependency names and interpreter paths. Raw name
+  bytes and string-table ranges retain observed identity where resolvable;
+  ranges include the terminating NUL and base64 bytes exclude it.
+- NOBITS and NULL sections provide no file bytes. Reported file-backed ranges
+  are checked against snapshot size again at the public boundary. PT_NULL payload
+  fields are unused: reported numbers remain, file backing is none and interpreted
+  permissions are null. Segments with zero file size also have no file bytes.
+- Sectionless dynamic images still report dependency names with raw bytes and
+  file locations where uniquely mapped. Missing symbol/relocation section tables
+  do not establish that those runtime tables are absent.
+  Upstream RELRO/canary heuristics rely on sections and can be incomplete in
+  this case; their reported candidates retain an explicit coverage limitation.
+- DT_NEEDED/PT_INTERP are reported names, not resolved runtime paths. GOT/PLT
+  maps are derived convenience views and may collapse aliases. PLT inference
+  can emulate selected instructions in Unicorn; its outputs are static candidates.
+  Exec syscall tracing observes host process launches. Map completeness
+  remains unknown and original upstream warnings are returned inline.
+- Canary, PIE, NX, executable-stack and RELRO are static inferences. NX and
+  executable-stack are separate upstream indicators: on x86-64 an executable
+  stack can accompany an unknown (`null`) NX indicator. ET_DYN can be a shared
+  library, and an absent canary symbol does not prove every function unprotected.
+
+Complete results have a 32 MiB input, 64 MiB reply, 1 MiB combined diagnostics
+and 30-second owned command deadline. The reply budget applies to the decoder
+record; the CLI/MCP Evidence envelope adds copies and encoding overhead. The
+pinned MCP SDK defaults to a 10 MiB receive buffer. Large complete results need
+a caller-configured `StdioClientTransport({ maxBufferSize: ... })`; the large
+extended-index verification uses 256 MiB and an explicit five-minute request
+timeout in its separate opt-in MCP lane. REA does not silently truncate the result. Python lowers resource soft limits to at most 3 GiB virtual address space,
+30 CPU seconds and 64 MiB file output. Inherited tighter soft/hard limits are
+retained, and the effective values are returned in the result limitations. Virtual address space is not RSS;
+Unicorn needs a large virtual map. Limits fail with no partial success, and
+owned process/root cleanup completes independently of cancellation.
+
+Core files, GDB session/state/control, optional pwndbg enrichment and instruction
+inspection are separate increments tracked by #969. This increment makes no
+real support claim for those features or other operating systems/architectures.
+
+Typed decoder failures retain bounded `captured_output` (stdout, stderr and an
+explicit truncation flag) alongside the original failure category and reason.
+Successful `diagnostics` also exposes the supervisor's `truncated` flag. Output
+beyond the complete diagnostic budget is rejected, including when the decoder
+writes a valid reply; cleanup and late cancellation reuse the observed flag.
+Memory allocation failures use `resource_constraint`, with effective resource
+limits (or an explicit unknown) and memory-specific recovery guidance. A
+MemoryError alone does not establish the exact failed allocation or that a
+particular budget was exhausted. Invalid undersized symbol entries are rejected
+before REA reports source ranges for them.
+The bridge reserves 1 MiB to report allocation failures. If even error reporting
+or serialization fails with MemoryError, its reserved exit status preserves the
+resource classification with unknown effective limits.
+Reserved exits require a matching private marker written by the bridge's actual
+failure branch. Bare launcher exits or missing/unwritable markers retain process
+diagnostics with the resource cause unverified.
+Signal termination alone is never classified as observed memory exhaustion.
+The small bootstrap also covers catchable MemoryError during adapter imports,
+compilation and initialization. Python interpreter startup failures before the
+bootstrap runs retain their observed process diagnostics without guessed causes.
+SIGXCPU retains a CPU resource diagnostic and CPU-specific recovery advice.
+Observed EFBIG writes or SIGXFSZ termination retain a file-size resource
+diagnostic and file-size-specific recovery advice. If a tight file limit also
+prevents writing the limit record, effective values remain unknown.
+The bridge records actual limits in owned storage before analysis; missing or
+malformed limit reports remain unknown with their read failure preserved. A
+received signal alone does not establish its exact cause. Dynamic tags require
+a complete DT_NULL inside PT_DYNAMIC; interpreter names and ranges end at the
+first NUL, with any padding still represented by the original segment range.