fix: bound the array subscript in LOCAL_PATH_RE so a hostile line stays linear

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -5,7 +5,7 @@
 **`sealed.local_path` now flags a home path inside a shell default, `${UBI_RUNNER:-/home/<user>…}`, as it already flagged the same path after `?? "/home/<user>…"` in TypeScript.** gstack-evals `quick/laneb/runner/launch.sh:9` passed the scan because the `-` before the path counted as part of a word (#3568).
 
 ### Fixed
-- **`sealed.local_path`** (`lib/sealed-guard.ts`): a home path directly after a `${…:-` or `${…-` default now matches, for a name, an array element (`${arr[0]:-`), an indirect name (`${!ref:-`), a positional number or a special parameter (`${@:-`). `:=`, `:+` and `:?` already matched, because `=`, `+` and `?` were never word characters. A hyphen anywhere else still excludes the match, so a path glued to a word (`docs-…`, `$VAR-…`, `${VAR}-…`) stays unflagged; docs/pregate.md lists that as a known limit.
+- **`sealed.local_path`** (`lib/sealed-guard.ts`): a home path directly after a `${…:-` or `${…-` default now matches, for a name, an array element (`${arr[0]:-`, a subscript of up to 64 characters, so a long line of unclosed `${a[` cannot make the scan quadratic), an indirect name (`${!ref:-`), a positional number or a special parameter (`${@:-`). `:=`, `:+` and `:?` already matched, because `=`, `+` and `?` were never word characters. A hyphen anywhere else still excludes the match, so a path glued to a word (`docs-…`, `$VAR-…`, `${VAR}-…`) stays unflagged; docs/pregate.md lists that as a known limit.
 
 ### Gate integrity
 - This is a gate edit that only tightens: the guard now refuses lines it passed before. No existing test, threshold or allowlist changed. A new case in `test/sealed-guard.test.ts` covers all five operators, a positional parameter, `${@`, an array element, an indirect name, a Windows path and the TypeScript `??` form. It also checks six negative controls: two hyphenated paths, a hyphenated sentence, `$VAR-`, `${VAR}-` and a relative default. Without the fix it misses every `-` form.

lib/sealed-guard.ts

@@ -43,7 +43,7 @@ export type Visibility = 'public' | 'private' | 'unknown';
 const KEYS = ['paths', 'transcripts', 'answer_markers', 'seed_patterns', 'local_paths', 'visibility'];
 const MAX_ENTRIES = 64;
 const MAX_REGEX = 256;
-const LOCAL_PATH_RE = /(?:^|[^A-Za-z0-9_.~-]|\$\{!?(?:[A-Za-z_][A-Za-z0-9_]*(?:\[[^\]\s]*\])?|[0-9]+|[@*#?$!-]):?-)(?:\/home\/[^/\s'"`]+\/|\/Users\/[^/\s'"`]+\/|[A-Za-z]:\\+Users\\+[^\\\s'"`]+\\)/;
+const LOCAL_PATH_RE = /(?:^|[^A-Za-z0-9_.~-]|\$\{!?(?:[A-Za-z_][A-Za-z0-9_]*(?:\[[^\]\s]{0,64}\])?|[0-9]+|[@*#?$!-]):?-)(?:\/home\/[^/\s'"`]+\/|\/Users\/[^/\s'"`]+\/|[A-Za-z]:\\+Users\\+[^\\\s'"`]+\\)/;
 const PUBLIC_TTL_MS = 24 * 3600_000;
 const PRIVATE_TTL_MS = 3600_000;