fix(3718): shell-free Node.js UI safety gate — fixes PowerShell silent-fail (#3718)

* fix(workflows): add word-boundary anchoring to UI safety gate grep

Replace unanchored grep -iE "UI |..." alternation with POSIX ERE
word-boundary-anchored form:

  LC_ALL=C grep -iE "(^|[^[:alnum:]])(UI|...)([^[:alnum:]]|$)"

Unanchored form matched 'ui' inside 'requirements', 'view' inside
'overview' and 'review', 'form' inside 'performance'/'platform'/
'transform' — producing HAS_UI=0 on 100% of standard roadmap phases
(every phase contains a **Requirements**: field).

Fix applied to both plan-phase.md:625 and autonomous.md:284.
LC_ALL=C added for POSIX locale portability on both BSD and GNU grep.

Closes #3706

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* test(workflows): add regression tests for UI safety gate false-positives (#3706)

- bug-3706-ui-safety-gate-false-positives.test.cjs: 36-test suite covering
  both plan-phase.md and autonomous.md gate behavior; verifies that
  Requirements/overview/performance/platform/transform/review/build/screening
  do NOT trigger the gate, while standalone UI/view/form/screen/dashboard/
  component/lowercase-ui/hyphenated-non-UI DO trigger it.

- autonomous-ui-steps.test.cjs: update stale assertion that checked for the
  old broken grep pattern; now asserts the word-boundary-anchored form.

Test strategy: extract the POSIX ERE pattern from the workflow file and
simulate grep match semantics in JS (no shell exec, no source-grep).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* chore(changeset): add Fixed fragment for PR #3718 (UI safety gate false-positives)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(workflows): document compound-token boundary contract; add comment to gate

Addresses adversarial review finding: word-boundary anchoring intentionally
does not match tokens embedded in compound alphanumeric words (e.g.
"microfrontend", "dashboardWidget", "uiSpec"). This is correct behavior —
gsd-roadmapper generates natural English prose, not camelCase compounds.
Hyphenated forms ("micro-frontend") and spaced forms are caught by the
anchored pattern (hyphen is [^[:alnum:]]).

Add inline comment in both workflow files explaining the pattern intent,
the false-positive prevention, and the compound-word contract.

Add 4 tests (2 per workflow) documenting the compound-word contract:
- "microfrontend" (compound) must NOT trigger gate (documented behavior)
- "micro-frontend" (hyphenated) MUST trigger gate (correct true-positive)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(3718): replace shell grep gate with shell-free Node.js helper

Moves UI safety gate logic from `LC_ALL=C grep -iE` (silently broken on
Windows PowerShell — locale env-var prefix not recognised by pwsh) to
`bin/lib/ui-safety-gate.cjs` (Node.js, reads via stdin to avoid ARG_MAX).

Path is anchored via `git rev-parse --show-toplevel` (GSD_REPO_ROOT) to
avoid CWD-sensitive failure when Claude Code executes from a subdirectory.

Word-boundary regex is identical to the original POSIX ERE pattern:
  (^|[^a-zA-Z0-9])(TOKEN)([^a-zA-Z0-9]|$)
Exit codes mirror grep: 0 = UI found, 1 = not found.

Tests: 51/51 pass — includes spawnSync shell:false + stdin cross-shell
portability tests and ARG_MAX large-input test.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix(3706): address pr-review-toolkit + codex review findings

- Multi-token-per-line: use matchAll to capture all UI tokens
- Add test for multiple distinct tokens on same line
- Clarify ASCII vs POSIX [:alnum:] in word-boundary comment
- Correct misleading "path anchored" comment in plan-phase/autonomous workflows
- Remove UI_GATE_PATTERN from module.exports (internal implementation detail)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

* fix(state): restore ACQUIRE_LOCK_RETRY_ERRNOS in acquireStateLock (#3718)

Commit 473c279c removed ACQUIRE_LOCK_RETRY_ERRNOS and replaced the
correct `throw err` path with `return lockPath`, which silently
"succeeds" on any non-EEXIST error — allowing two concurrent processes
to both hold the lock simultaneously and causing lost updates.

This restores the set of recoverable transient errno codes (Docker
overlay-fs EINVAL/EIO/ENOENT, NFS ESTALE, POSIX EAGAIN/EINTR, Windows
EPERM/EBUSY) that should retry, and restores `throw err` for genuinely
fatal codes.  Equivalent to commit 47983914 on main.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>