feat(miner-ui): add an optional ORB/Grafana footer link to the root layout

[davion-knight]

Renders a footer link to an operator-configured ORB/Grafana dashboard in the miner-ui root layout (#5194). (Resubmit — fixes the empty-footer defect below.)

Fix vs the prior submission (#5401, closed on review)

The prior version put the <footer className="…py-4…"> wrapper in __root.tsx unconditionally, so when VITE_MINER_UI_GRAFANA_URL was unset the inner component returned null but an empty, padded footer still rendered — violating "render nothing when unset." Now GrafanaFooterLink owns the whole <footer> and returns null for all of it when unset; __root.tsx just renders <GrafanaFooterLink />. No empty wrapper.

Behavior (matches the issue)

• One optional VITE_-prefixed env var (VITE_MINER_UI_GRAFANA_URL) — Vite only exposes VITE_* to the client bundle.
• Renders the footer+link only when set and non-empty; nothing at all (no footer element, no placeholder) when unset.
• New tab (target="_blank" rel="noopener noreferrer"); URL rendered verbatim as a plain href (React-escaped, no injection); no token/credential ever appended.
• No other footer/layout/auth logic changed; documented in the miner-ui README.

Validation

• src/grafana-footer-link.test.tsx (3 tests): env-set → a <footer> (contentinfo) with the correctly-attributed link; env-unset → NO footer wrapper at all (queryByRole("contentinfo") is null — the exact regression); href-verbatim invariant (no credential appended).
• tsc clean (my files); prettier-clean; no secrets. apps/** is codecov-ignored (codecov/patch vacuous).

Closes #5194

[superagent-security]

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

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✅ Gittensory review result - approve/merge recommended

_{Review updated: 2026-07-12 18:59:14 UTC}

4 files · 1 AI reviewer · no blockers · readiness 100/100 · CI green · clean

✅ Suggested Action - Approve/Merge

• safe to merge

Review summary
This PR adds a GrafanaFooterLink component that owns its entire <footer> wrapper and returns null when VITE_MINER_UI_GRAFANA_URL is unset, correctly fixing the empty-padded-footer regression from the prior closed PR #5401. The implementation is simple, correctly scoped to the linked issue #5194, uses the required VITE_ prefix for client exposure, and includes tests covering both the set and unset states plus a verbatim-href/no-credential-leak check. The URL is rendered as a plain href attribute which React escapes, so no injection risk from a misconfigured value.

Nits — 5 non-blocking

• grafana-footer-link.tsx has no href scheme validation, so a misconfigured env var like `javascript:alert(1)` would technically render, though this is operator-controlled config rather than user input so the risk is minimal.
• The component doesn't trim the url before the truthiness check, so a value of whitespace-only string (e.g. " ") would pass `!url` and render a broken/blank link — worth a `.trim()` guard for defensive hardening.
• Consider trimming and validating the URL scheme (http/https) in grafana-footer-link.tsx before rendering, to guard against obviously malformed operator config.
• The README table formatting is a bit wide/unaligned for the long description cell — could wrap or shorten for readability, purely stylistic.
• nit: apps/gittensory-miner-ui/src/components/grafana-footer-link.tsx:1 has a long explanatory header comment that repeats the README and tests; I would trim this to the env-var contract plus the empty-render invariant so the component stays easier to scan.

Signal	Result	Evidence
Code review	✅ No blockers	1 reviewer
Linked issue	✅ Linked	#5194
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: 124 registered-repo PR(s), 89 merged, 2 issue(s).
Contributor context	✅ Confirmed Gittensor contributor	davion-knight; Gittensor profile; 124 PR(s), 2 issue(s).
Gate result	✅ Passing	No configured blocker found.
Improvement	✅ Minor	risk: clean · value: minor — Code changes are accompanied by test evidence.

Review context

• Author: davion-knight
• Role context: outside_contributor
• Public audience mode: oss maintainer
• Lane context: Repository is configured for direct PR review.
• Public profile languages: not available
• Official Gittensor activity: 124 PR(s), 2 issue(s).
• PR-specific overlap: none found.

Contributor next steps

• Keep the PR focused and include validation evidence before maintainer review.

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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