fix(ci): repair e2e.yml Zig + Deno pins (baseline rot) (#123)

## Summary

Restores three CI checks to green by repairing two unrelated upstream
pin issues in `.github/workflows/e2e.yml`. All three had been red on
`main`, gating every PR:

- `E2E — Full REST + MCP Bridge`
- `E2E — Order Ticket (FFI layer)`
- `Bench — FFI Catalogue + Mount/Unmount + Hash`

## Fixes

1. **Zig `0.15.0` retired upstream.** All three `setup-zig` steps failed
on `Error: Could not find version 0.15.0 for platform x86_64-linux`.
Bumped to `0.15.1` to match `.tool-versions` (the canonical estate
declaration). `release.yml` runs `0.15.2` via `mlugg/setup-zig`; either
point on the 0.15.x line is fine.

2. **`denoland/setup-deno` SHA `5fae568d…` no longer resolves.** GitHub
Actions: `Unable to resolve action
denoland/setup-deno@5fae568`. Repointed
to the same v2.0.4 SHA already in use by `publish.yml`
(`667a34cdef165d8d2b2e98dde39547c9daac7282`), verified via the GitHub
API.

## Relationship to #118

Companion to **#118** (`tests/aspect_tests.sh` grep-count fix). The two
were originally one commit but workflow-file edits need the `workflow`
OAuth scope to push, so they're split.

## Out of scope (deliberately)

`governance / Language / package anti-pattern policy` is also red on
main, but a parallel session is already diagnosing it under the
Estate-drift-remediation 2026-05 campaign (parent standards#66). Not
touched here per the parallel-session-branch-drift guardrail.

## Test plan

- [ ] CI on this PR: the three previously-red checks (E2E Full, E2E
Order Ticket, Bench) come back green.
- [ ] No new reds introduced by the Zig version bump.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: hyperpolymath

.github/workflows/e2e.yml

@@ -49,10 +49,10 @@ jobs:
       - name: Install Zig
         uses: goto-bus-stop/setup-zig@9566bb3e8749893055694249726756f25e099b30  # v2
         with:
-          version: 0.15.0
+          version: 0.15.1
 
       - name: Install Deno
-        uses: denoland/setup-deno@5fae568d37c3b73e0e4ca63d4e2c4e324a2b3497  # v2
+        uses: denoland/setup-deno@667a34cdef165d8d2b2e98dde39547c9daac7282  # v2.0.4
         with:
           deno-version: v2.x
 
@@ -90,7 +90,7 @@ jobs:
       - name: Install Zig
         uses: goto-bus-stop/setup-zig@9566bb3e8749893055694249726756f25e099b30  # v2
         with:
-          version: 0.15.0
+          version: 0.15.1
 
       - name: Build FFI libraries
         run: cd ffi/zig && zig build
@@ -124,7 +124,7 @@ jobs:
       - name: Install Zig
         uses: goto-bus-stop/setup-zig@9566bb3e8749893055694249726756f25e099b30  # v2
         with:
-          version: 0.15.0
+          version: 0.15.1
 
       - name: Build FFI libraries
         run: cd ffi/zig && zig build