fix(integrations): project-tracker-adapter.ts's parseRepoFullName is missing the whitespace guard every sibling has

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⚠️ Definition of Done: this issue must be completed in full, in a single PR. Do not split this
work across multiple PRs, and do not defer any Deliverable below to a follow-up issue. A PR that
satisfies only some of the Deliverables, stubs a required test, or leaves a checkbox
partially-done does NOT resolve this issue and will be closed.

Context

Mirror this fix exactly: #8311 (fix(github): app.ts/comments.ts repoFullName parsing is missing the segment-count/whitespace guard every sibling GitHub-write module has) established the
segment-count + whitespace repoFullName guard as the required convention across every
src/github/*.ts write/read module. This issue applies the identical fix to
src/integrations/project-tracker-adapter.ts's own parseRepoFullName, which never adopted it.

The established guard, quoting one of the six existing copies (src/github/labels.ts:9-19):

function parseRepoFullName(repoFullName: string): { owner: string; repo: string } {
  const parts = repoFullName.split("/");
  const owner = parts[0];
  const repo = parts[1];
  if (parts.length !== 2 || !owner || !repo || /\s/.test(repoFullName)) {
    throw new Error(`Invalid repository full name: ${repoFullName}`);
  }
  return { owner, repo };
}

src/integrations/project-tracker-adapter.ts:39-46 has its own, differently-named-but-same-purpose
parseRepoFullName:

function parseRepoFullName(repoFullName: string): { owner: string; repo: string } {
  const parts = repoFullName.split("/");
  const owner = parts[0];
  const repo = parts[1];
  if (parts.length !== 2 || !owner || !repo) {
    throw new Error(`Invalid repository full name: ${repoFullName}`);
  }
  return { owner, repo };
}

This is the partial case #8311 explicitly named for comments.ts: it already has the
segment-count guard, but is missing the /\s/.test(repoFullName) whitespace check that
pr-actions.ts/assignees.ts/labels.ts/app.ts/comments.ts all now have. A repo name like
"owner/ repo" (embedded whitespace) currently passes this check and gets encodeURIComponent-ed
straight into a GitHub REST URL (GitHubMilestonesAdapter.listOpenMilestones/attachToMilestone)
or interpolated into a GraphQL login variable (GitHubProjectsAdapter.listOpenProjects) —
exactly the failure mode #8311 closed everywhere else.

Requirements

• parseRepoFullName in src/integrations/project-tracker-adapter.ts:39-46 must additionally
  reject any repoFullName containing whitespace (/\s/.test(repoFullName)), matching the
  pr-actions.ts/assignees.ts/labels.ts convention #8311 extended to app.ts/comments.ts.
• The existing failure contract (throwing Error("Invalid repository full name: ...")) must be
  preserved exactly — only the validation condition gets stricter, not the failure shape.
• This is a one-line change to an existing local helper — do not introduce a shared cross-file
  helper; this file already correctly keeps its own local copy per the established house
  convention.

Deliverables

• parseRepoFullName (src/integrations/project-tracker-adapter.ts:39-46) additionally
  rejects a repoFullName containing whitespace.
• A regression test in test/unit/project-tracker-adapter.test.ts asserting
  "owner/ repo" (and/or " owner/repo") is rejected the same way the existing malformed-input
  case(s) already are, mirroring the coverage pattern used for the sibling guard in
  test/unit/github-pr-actions.test.ts/github-assignees.test.ts/github-labels.test.ts.

All of the above Deliverables are required in the same PR.

Test Coverage Requirements

99%+ Codecov patch coverage, branch-counted, on the changed line and its new branch in
src/integrations/project-tracker-adapter.ts.

Expected Outcome

src/integrations/project-tracker-adapter.ts rejects the same malformed repoFullName shapes
(embedded whitespace) that every src/github/*.ts write/read module already rejects since
#8311, with no behavior change for any well-formed owner/repo value.

Links & Resources

• #8311 (the prior, closed instance of this exact bug class for src/github/)
• src/github/labels.ts:9-19 (a full, current copy of the required guard, to mirror)
• src/integrations/project-tracker-adapter.ts:39-46 (the module's own partial copy, to fix)
• test/unit/project-tracker-adapter.test.ts (existing coverage — has no whitespace-rejection
  test for this helper)

[linear-code]

JSO-6473