* fix(skillscan): match fork bombs by shape, not spelling
`resource-fork-bomb` and the fork-bomb branch of `shell-destructive-command`
only matched the canonical `:(){ :|:& };:` rendering, so renamed or respaced
payloads produced no findings and passed the blocking gate.
Match the general shape instead - a shell function whose body recurses through
a pipe into a background job - keeping the pre-LLM static gate at least as
wide as the runtime sandbox audit middleware it backstops.
Closes#6651.
* fix(skillscan): bound the fork-bomb pattern and require self-recursion
Addresses the three review findings on #6689:
- Bound every quantifier in the shared fork-bomb pattern so a whitespace-free
blob costs O(n) instead of O(n^2) (measured ~0.15s at 200KB; the previous
spelling took ~5.5s at just 50KB).
- Require the function name to recur after the pipe (backreference), so a
benign pipeline such as `backup() { rsync -a src/ | logger & }` no longer
blocks as a CRITICAL finding.
- Keep both gates byte-identical again: skillscan's _FORK_BOMB_PATTERN and the
sandbox_audit_middleware fork-bomb entry, pinned by a parity test.
- The code comment now describes exactly what the pattern checks; pipe-less
self-backgrounding recursion and the spaced `|&` spelling are documented as
out of scope.
- New regression tests: near-miss pipelines in both suites, the parity
invariant, and a 200KB single-token scan-time ceiling.
---------
Co-authored-by: Willem Jiang <willem.jiang@gmail.com>
