fix(session): report a missing Linux ps as provider unavailability in status (#7180)

Keep binary_session available when Linux owned-child probes lack procps ps. Preserve typed ownership-prerequisite failures in direct execution and report per-provider readiness in status. Independently validated on latest main through real stdio MCP plus focused regression, static and documentation checks. Closes #7164.

docs/installation.md

@@ -412,6 +412,13 @@ The public error code varies by caller: `capability_unavailable`,
 only a generic startup error. Check this prerequisite before following
 provider-specific recovery advice.
 
+`binary_session` still returns status on such a host. Providers whose
+readiness check reaches the owned-child launch, such as Ghidra's Java probe,
+JADX and Apktool, report themselves unavailable with a reason naming the
+missing `ps`. A provider that fails an earlier configuration check, such as
+JADX without `REA_JADX_MCP_JAR`, keeps that reason. The other providers keep
+their own status. `open_binary` keeps the refusal described above.
+
 ## Diagnose, update, and remove
 
 `rea doctor --json` is strictly read-only. `rea update` updates only the npm or Bun global installation that owns the running CLI. Source checkouts and package-runner copies must be updated through the mechanism that owns them; a fresh package-runner invocation can use `npx rea-agents@latest` or `bunx rea-agents@latest`. `rea uninstall` removes only REA-owned agent registrations and skill files; `--purge-data` additionally removes REA cache and state paths.