test: consent-gate E2E suite + functional fs-capability probes

Five hermetic gate-tier E2E cases (tpa-present / absent-linux / broken /
absent-darwin / apple-ban) drive the real contract section through
claude -p with PATH shims for aside and uname; the absent cases filter
any REAL aside binary out of the child PATH and assert absence with
Bun.which before spawning, so dev machines cannot leak into detection.
Registered per-case in E2E_TOUCHFILES/E2E_TIERS with template-level
deps (ship/SKILL.md.tmpl, gen-skill-docs.ts) and added to the evals.yml
matrix with tier: gate. eval:bg:periodic's detach timeout rises to
36000s for the grown periodic shard census (floor-enforced by
test/eval-detach-timeout-floor.test.ts); CLAUDE.md doc updated to match.

test/helpers/fs-caps.ts adds canRevokeWrites/canRevokeReads functional
probes; 13 chmod-based tests swap their uid-0-only guards for the
probes so suites skip honestly on CAP_DAC_OVERRIDE containers (this
sandbox: uid 1000 with full caps) instead of asserting revocations the
kernel ignores. path-validation's symlink test targets /etc/passwd
(exists everywhere; /etc/crontab is absent on Amazon Linux).

CLAUDE.md

@@ -634,7 +634,7 @@ the run can also die to idle-sleep. `gstack-detach` fixes both: a fresh session
   (stray `claude`/`codex` grandchildren included), a per-shard
   `GSTACK_EVAL_DIR=<evalDir>/shards/<slug>/` honored by the `EvalCollector`
   constructor, and an aggregate that separates failed vs timed-out vs
-  never-started shards — the detach timeouts (25200s gate / 32400s periodic;
+  never-started shards — the detach timeouts (25200s gate / 36000s periodic;
   floor enforced against the live shard census by
   test/eval-detach-timeout-floor.test.ts)
   are sized against worst-case shard wall clock. `EVALS_JOBS` sets the shard