fix(codex): retire deprecated web-search flag behind one CODEX_WEB_SEARCH_FLAG constant (#2525)

codex >=0.144 deprecates the legacy --enable-based web_search_cached
spelling (web search is on by default; --enable <FEATURE> now means
-c features.<name>=true, verified against codex 0.147.0's exec --help).
Every gstack codex invocation now passes -c 'web_search="cached"' instead.

The flag previously lived inline at 19 raw sites. Per ENG-OV11a the 10
template-inline sites (autoplan/SKILL.md.tmpl x4, codex/SKILL.md.tmpl x6)
convert to a shared {{CODEX_WEB_SEARCH_FLAG}} token first, so ONE resolver
constant (CODEX_WEB_SEARCH_FLAG in scripts/resolvers/constants.ts) now
covers all sites: review.ts x5, design.ts x3, the token resolver in
utility.ts, and the tool-map helper comment.

codex/SKILL.md.tmpl's web-search prose guarantee is corrected: the -c form
explicitly overrides a top-level web_search config (the legacy flag yielded
to it), and native codex review disables web search regardless of
configuration, so the flag is a no-op on the default Review path.

test/codex-web-search-flag.test.ts is the safety net: repo-wide grep
tripwires assert NO rendered SKILL.md/section/golden and NO source file
carries the deprecated spelling, and that the token resolves in rendered
output.

Fixes #2525

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

review/SKILL.md

@@ -1734,7 +1734,7 @@ _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo"
 # here. It defines _gstack_codex_timeout_wrapper (gtimeout -> timeout ->
 # unwrapped fallback), added in #1056 but never wired into this call site.
 source ~/.claude/skills/gstack/bin/gstack-codex-probe 2>/dev/null || true
-_gstack_codex_timeout_wrapper 540 codex exec "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. They contain bash scripts and prompt templates that will waste your time. Ignore them completely. Do NOT modify agents/openai.yaml. Stay focused on the repository code only.\n\nReview the changes on this branch against the base branch. Run DIFF_BASE=$(git merge-base origin/<base> HEAD) && git diff "$DIFF_BASE" to see the diff. Your job is to find ways this code will fail in production. Think like an attacker and a chaos engineer. Find edge cases, race conditions, security holes, resource leaks, failure modes, and silent data corruption paths. Be adversarial. Be thorough. No compliments — just the problems. End your output with ONE line in the canonical format `Recommendation: <action> because <one-line reason naming the most exploitable finding>`. Generic reasons like 'because it's safer' do not qualify; the reason must point to a specific finding or no-fix rationale." -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="high"' --enable web_search_cached < /dev/null 2>"$TMPERR_ADV"
+_gstack_codex_timeout_wrapper 540 codex exec "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. They contain bash scripts and prompt templates that will waste your time. Ignore them completely. Do NOT modify agents/openai.yaml. Stay focused on the repository code only.\n\nReview the changes on this branch against the base branch. Run DIFF_BASE=$(git merge-base origin/<base> HEAD) && git diff "$DIFF_BASE" to see the diff. Your job is to find ways this code will fail in production. Think like an attacker and a chaos engineer. Find edge cases, race conditions, security holes, resource leaks, failure modes, and silent data corruption paths. Be adversarial. Be thorough. No compliments — just the problems. End your output with ONE line in the canonical format `Recommendation: <action> because <one-line reason naming the most exploitable finding>`. Generic reasons like 'because it's safer' do not qualify; the reason must point to a specific finding or no-fix rationale." -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR_ADV"
 ```
 
 Set the Bash tool's `timeout` parameter to `600000` (10 minutes). It sits ABOVE the 540s wrapper deliberately, so the wrapper fires first and a stall surfaces as a diagnosable exit 124 instead of a harness kill that returns nothing. The wrapper resolves `gtimeout`, then `timeout`, then runs unwrapped, so it is safe on a macOS without coreutils. After the command completes, read stderr:
@@ -1767,7 +1767,7 @@ cd "$_REPO_ROOT"
 # here. It defines _gstack_codex_timeout_wrapper (gtimeout -> timeout ->
 # unwrapped fallback), added in #1056 but never wired into this call site.
 source ~/.claude/skills/gstack/bin/gstack-codex-probe 2>/dev/null || true
-_gstack_codex_timeout_wrapper 540 codex review --base <base> -c 'model_reasoning_effort="high"' --enable web_search_cached < /dev/null 2>"$TMPERR"
+_gstack_codex_timeout_wrapper 540 codex review --base <base> -c 'model_reasoning_effort="high"' -c 'web_search="cached"' < /dev/null 2>"$TMPERR"
 ```
 
 **No prompt argument.** `--base` is what scopes the review, and the positional `[PROMPT]` is mutually exclusive with it — passing both fails at argv parsing. Do NOT "fix" that error by dropping `--base` and keeping the prompt: a prompt-only `codex review` silently falls back to the **uncommitted working-tree** scope (`git status --short; git diff`), so it reviews the wrong changes and reports "no changes" on a clean tree. Prompt text describing the diff range does not change what the CLI feeds the reviewer. Unlike the adversarial pass above, which uses `codex exec` and really does run the git command it's told to, this path gets a pre-computed diff from the CLI — which is also why it needs no filesystem boundary.