test(ui): add coverage for use-api-session.ts (#7903)

[xfodev]

Closes #7903

What

apps/ui/src/hooks/use-api-session.ts — the wallet-signature challenge → sign → verify session hook (sessionStorage-persisted, address-scoped, expiry-checked) — had zero test coverage. This adds it.

How

This suite is plain-node (no DOM, no renderHook — see apps/ui/vitest.config.ts, and no hook test in the repo renders), so I cover the hook's real logic through its two extracted, exported pure pieces — matching the repo's "test the extracted pure function" convention (e.g. use-move-stake-flow):

• readStoredSession / writeStoredSession — the address-scoped, expiry-checked sessionStorage helpers (added export).
• performWalletSignIn(wallet, deps) — the challenge → sign → verify → session-shape orchestration, split out of signIn with apiFetch / signMessage / now dependency-injected so it's testable without a DOM. The hook's signIn now delegates to it; behavior is unchanged.

Tests — apps/ui/src/hooks/use-api-session.test.ts (10 cases)

• performWalletSignIn: the full challenge→sign→verify flow (asserts the POST paths/bodies, the signer call, and the shaped session incl. expiresAtMs = now + expires_in*1000); ApiError propagation.
• readStoredSession / writeStoredSession: round-trip, wrong-address rejection, expired rejection, empty, malformed-JSON (never throws), storage-throws (never throws), clear-on-null, and the SSR no-window no-op.

Scoped to apps/ui/src/hooks/ — no visual/component change, so it follows the normal (non-screenshot-gated) review path per the frontend contribution rules.

• npx vitest run src/hooks/use-api-session.test.ts — 10 passed
• eslint + prettier clean; typecheck clean for these files
• Links a tracked, currently-open issue (Closes #7903)

[superagent-security]

Superagent didn't find any vulnerabilities or security issues in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.58%. Comparing base (487ef64) to head (778d1e0).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7955   +/-   ##
=======================================
  Coverage   97.58%   97.58%           
=======================================
  Files         204      204           
  Lines       26365    26365           
  Branches    10452    10452           
=======================================
  Hits        25729    25729           
  Misses        150      150           
  Partials      486      486           

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[loopover-orb]

Warning

⏸️ LoopOver review result - manual review recommended

_{Review updated: 2026-07-24 16:21:17 UTC}

2 files · 1 AI reviewer · no blockers · CI green · clean

⏸️ Suggested Action - Manual Review

• Touches a guarded path — held for manual review: This PR changes guardrail-protected path(s): apps/ui/src/hooks/use-api-session.test.ts (matched apps/ui/**), apps/ui/src/hooks/use-api-session.ts (matched apps/ui/**).

Review summary
The AI review returned non-blocking notes for this change but did not include a separate narrative summary. Review the nits below before deciding this PR.

Nits — 4 non-blocking

• `beforeEach` is imported in the test file but never used, which is dead import clutter.
• Remove the unused `beforeEach` import in apps/ui/src/hooks/use-api-session.test.ts:1.
• Consider a test asserting `writeStoredSession`'s catch-swallow path (setItem throwing) mirrors the read-side 'storage throws' coverage for full symmetry.
• Touches a guarded path — held for manual review — A maintainer must review and merge this change.

Decision drivers

• ✅ Code review — No blockers (1 reviewer)
• ⚠️ Gate result — Not blocking (Advisory; not blocking this PR.)

Context & advisory signals — never blocks the verdict

Signal	Result	Evidence
Linked issue	✅ Linked	#7903
Related work	✅ No active overlap found	No same-issue or scoped active PR overlap found.
Change scope	✅ 20/20	Low review scope from cached public metadata (1 linked issue).
Validation posture	✅ 25/25	PR body includes validation/test evidence.
Contributor workload	✅ 10/10	Author activity: 64 registered-repo PR(s), 29 merged, 0 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	xfodev; Gittensor profile; 64 PR(s), 0 issue(s).

Review context

• Author: xfodev
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: JavaScript, TypeScript
• Official Gittensor activity: 64 PR(s), 0 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Start here: Triage stale or unlinked PRs.

Signal definitions

• Related work = same linked issue, overlapping active PRs, or title/path similarity.
• Change scope = cached public metadata such as size labels, draft state, and review-burden hints.
• Validation posture = whether the PR provides enough public validation/test evidence for maintainer review.
• Contributor workload = public contributor activity and cleanup pressure, not a repo-wide quality failure.
• Contributor context = public GitHub/Gittensor identity context; non-Gittensor status is not a blocker.

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_{🟩 Safe / merged · 🟦 Advisory · 🟨 Held for review · 🟥 Blocked / closed}

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