Remove linked-issue gate from commitperclip (#7423)

## Thinking Path

> - Paperclip orchestrates AI agents for zero-human companies
> - The `commitperclip` PR quality gates enforce hygiene on every PR
before merge
> - One of those gates required PRs to link to a tracking issue, which
adds friction for small/internal changes that don't need a tracker entry
> - The repository owner decided the linked-issue requirement is no
longer the right default
> - This pull request removes the linked-issue gate (the script, its
tests, and the orchestrator wiring)
> - The benefit is fewer false-failing PR checks and one less mandatory
authoring step

## What Changed

- Deleted `.github/scripts/check-pr-linked-issue.mjs`
- Deleted `.github/scripts/tests/check-pr-linked-issue.test.mjs`
- Removed the `checkLinkedIssue` import, the
`Promise.resolve(checkLinkedIssue(...))` entry in the `Promise.all`
block, the `issueResult` destructured binding, and the
`...issueResult.failures` spread from
`.github/scripts/run-quality-gates.mjs`

## Verification

- `node --test .github/scripts/tests/*.test.mjs` — 72/72 tests pass
across the remaining 4 gate suites
- `git grep -n
'check-pr-linked-issue\|checkLinkedIssue\|check-pr-linked'` — no matches
- Inspected `run-quality-gates.mjs` — no orphaned `issueResult`
references

## Risks

- Low risk. Pure removal of one optional gate; the
`.github/workflows/commitperclip-review.yml` workflow only invokes the
orchestrator and needs no changes. PR template and `CONTRIBUTING.md` do
not mention linked issues, so no docs change is required.

## Model Used

- Claude (Anthropic), `claude-opus-4-7`, extended-thinking mode, tool
use enabled

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable (existing
gate-suite tests still pass; removed gate's tests deleted with it)
- [x] If this change affects the UI, I have included before/after
screenshots (n/a — CI script change)
- [x] I have updated relevant documentation to reflect my changes (no
docs reference the removed gate)
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

Co-authored-by: Paperclip <noreply@paperclip.ing>

.github/scripts/run-quality-gates.mjs

@@ -11,7 +11,6 @@ import { fileURLToPath } from 'node:url';
 import { ghFetch } from './get-bot-token.mjs';
 import { fetchAllPullRequestFiles } from './fetch-pr-files.mjs';
 import { checkTemplate } from './check-pr-template.mjs';
-import { checkLinkedIssue } from './check-pr-linked-issue.mjs';
 import { checkTestCoverage } from './check-pr-test-coverage.mjs';
 import { checkLockfile } from './check-pr-lockfile.mjs';
 import { checkDependencies } from './check-pr-dependencies.mjs';
@@ -110,10 +109,9 @@ async function main() {
 
   // Run all quality gates (pure functions run sync, deps check is async)
   const prTitle = pr.title ?? '';
-  const [templateResult, issueResult, testResult, lockfileResult, depsResult] =
+  const [templateResult, testResult, lockfileResult, depsResult] =
     await Promise.all([
       Promise.resolve(checkTemplate(prBody)),
-      Promise.resolve(checkLinkedIssue(prBody, prTitle)),
       Promise.resolve(checkTestCoverage(files, prTitle)),
       Promise.resolve(checkLockfile(files, author, branch)),
       checkDependencies(files, GH_TOKEN, GH_REPO, prNumber, pr.base?.ref),
@@ -121,7 +119,6 @@ async function main() {
 
   const allFailures = [
     ...templateResult.failures,
-    ...issueResult.failures,
     ...testResult.failures,
     ...lockfileResult.failures,
   ];