feat(process): make the regex worker heap request configurable (#6301)

* feat(process): make the regex worker heap request configurable

REA_REGEX_WORKER_HEAP_REQUEST_MIB keeps the 128 MiB default and refuses
values outside 8 to 16384 MiB. A positive Node --max-old-space-size still
overrides the request and is not clamped by the setting.

Co-authored-by: morluto <morluto@users.noreply.github.com>

* fix(process): set the regex worker heap floor to the measured startup bound

On Node 22.23.4 a 5 MiB old-generation request aborts the regex worker
during startup, and 6 MiB starts it and returns a match. The setting floor
is that measured bound.

Co-authored-by: morluto <morluto@users.noreply.github.com>

* fix(process): raise the regex worker heap floor to 7 MiB

6 MiB passes configuration but returns ERR_WORKER_OUT_OF_MEMORY for a
trivial match on supported Linux Node 24 and Node 26.0.0. 7 MiB returned
that match on the measured 22, 24, and 26 lines. A clean-process test
runs the production worker at the floor.

Co-authored-by: morluto <morluto@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: morluto <morluto@users.noreply.github.com>

docs/kuna-provider.md

@@ -68,7 +68,7 @@ The background export belongs to the session. `close_binary`, or the end of a CL
 
 The assembly label index is scanned once per export reader. Cancelling a request stops its wait without interrupting other readers; closing the session aborts and drains the shared scan before releasing its files.
 
-Regex procedure and string search uses ECMAScript Unicode matching in a cancellable worker with a matching deadline and a worker old-generation heap. Literal matching remains the default. Cancellation or a matching deadline leaves the session available. The deadline is `REA_REGEX_MATCHING_DEADLINE_MS`, a positive decimal integer from 1 to 2147483647 ms. Unset uses 5000 ms. A larger value is refused because Node schedules a delay past that signed 32-bit bound as 1 ms. Invalid values are configuration errors and do not fall back to the default. The setting is read from the environment that starts REA, so a change needs a restart. A deadline failure names the effective milliseconds, whether they came from the default or the setting, the default, and the maximum. The worker old-generation heap does not raise it. The worker requests 128 MiB. A positive Node.js `--max-old-space-size` on the process that starts REA, including `NODE_OPTIONS`, overrides that request and sets the effective heap. `--max-old-space-size-percentage` takes precedence over that flag in either order. REA does not turn the percentage into a MiB, so the effective heap stays unestablished instead of the 128 MiB request or the absolute flag. The reported `NODE_OPTIONS` value is the process initial environment when that block can be read. A later edit to the environment is not the value Node applied, and an unreadable initial value leaves the effective heap unestablished. The launch Node options are the initial command line on Linux when that buffer still has a program entry, not a later edit to `process.execArgv`. A preload can clear that array after V8 has applied the flags. Setting `process.title` or `--title` overwrites the command line, so a buffer without a program entry leaves the effective heap unestablished. `--env-file` or `--env-file-if-exists` can supply `NODE_OPTIONS` when the initial environment has none. That file is not part of the initial environment block, so the effective heap stays unestablished instead of the 128 MiB request. An initial `NODE_OPTIONS` is still used, because Node does not let the file replace it. A positive `--max-heap-size`, including the underscore form and launch `NODE_OPTIONS` on Node versions that allow it, sets the total heap rather than the old generation and can be lower than the 128 MiB request. The effective old generation stays unestablished while that value is in effect. A zero or empty value clears it. `--experimental-config-file` or `--experimental-default-config-file` can set `nodeOptions`, including a heap percentage, from a file that is not read back. The effective heap stays unestablished when either flag is present, including when an absolute `--max-old-space-size` is also on the command line or in the recovered `NODE_OPTIONS`. Node accepts the config path as `=` or the next argument.
+Regex procedure and string search uses ECMAScript Unicode matching in a cancellable worker with a matching deadline and a worker old-generation heap. Literal matching remains the default. Cancellation or a matching deadline leaves the session available. The deadline is `REA_REGEX_MATCHING_DEADLINE_MS`, a positive decimal integer from 1 to 2147483647 ms. Unset uses 5000 ms. A larger value is refused because Node schedules a delay past that signed 32-bit bound as 1 ms. Invalid values are configuration errors and do not fall back to the default. The setting is read from the environment that starts REA, so a change needs a restart. A deadline failure names the effective milliseconds, whether they came from the default or the setting, the default, and the maximum. The worker old-generation heap does not raise it. The worker heap request is `REA_REGEX_WORKER_HEAP_REQUEST_MIB`, a decimal integer from 7 to 16384 MiB. Unset uses 128 MiB. A request below 7 MiB aborts the worker during startup, and a larger value is refused. Invalid values are configuration errors and do not fall back to 128. The setting is read from the environment that starts REA, so a change needs a restart. A heap failure names the effective request, whether it came from the default or the setting, the default, the floor, and the maximum. A positive Node.js `--max-old-space-size` on the process that starts REA, including `NODE_OPTIONS`, overrides that request and sets the effective heap. `--max-old-space-size-percentage` takes precedence over that flag in either order. REA does not turn the percentage into a MiB, so the effective heap stays unestablished instead of the worker heap request or the absolute flag. The reported `NODE_OPTIONS` value is the process initial environment when that block can be read. A later edit to the environment is not the value Node applied, and an unreadable initial value leaves the effective heap unestablished. The launch Node options are the initial command line on Linux when that buffer still has a program entry, not a later edit to `process.execArgv`. A preload can clear that array after V8 has applied the flags. Setting `process.title` or `--title` overwrites the command line, so a buffer without a program entry leaves the effective heap unestablished. `--env-file` or `--env-file-if-exists` can supply `NODE_OPTIONS` when the initial environment has none. That file is not part of the initial environment block, so the effective heap stays unestablished instead of the worker heap request. An initial `NODE_OPTIONS` is still used, because Node does not let the file replace it. A positive `--max-heap-size`, including the underscore form and launch `NODE_OPTIONS` on Node versions that allow it, sets the total heap rather than the old generation and can be lower than the worker heap request. The effective old generation stays unestablished while that value is in effect. A zero or empty value clears it. `--experimental-config-file` or `--experimental-default-config-file` can set `nodeOptions`, including a heap percentage, from a file that is not read back. The effective heap stays unestablished when either flag is present, including when an absolute `--max-old-space-size` is also on the command line or in the recovered `NODE_OPTIONS`. Node accepts the config path as `=` or the next argument.
 
 Single-function subprocess output and each cached source facet share a 16 MiB buffered-text capacity. Cached spans are checked before allocation; larger text remains in the local export and the error identifies the file and range. `analyze_function` initially returns the complete dossier, which can still be large; later retained views do not remove that first transfer. Prefer the individual text tools for a focused question.