feat(status-pages): dashboard tab and editor - #1932

🟡 Confidence 6/10 · needs attention. Held at 6 because a correctness warning is open.
_{2 warnings −2 · 7 notes · tests covered · risk medium · 8 defects fixed in earlier rounds}

Adds the Status pages tab to the alerts hub and the /alerts/status-pages/<id> editor with components, incidents and settings tabs. Safe to merge apart from the nine findings carried over from earlier reviews, none of which this head fixes. The pre-existing McpQueryError issues surfacing through apps/web/src/page/registry.ts are untouched: the diff only registers one more lazy page there.

• /alerts?tab=status-pages lists pages with worst status, open incidents and publish state
• /alerts/status-pages/<id> editor with components, incidents and settings tabs
• Incidents composer, post-update and resolve flows; maintenance windows read in the viewer's zone
• Break-glass token issue, replace and revoke, plus settings save bar and page delete

Still open from earlier reviews

• 🟠 Warning · F12 · A non-empty name with no ASCII letters or digits yields an empty slug, and slugError is suppressed for the empty slug so the disabled Create button has no explanation · apps/web/src/page/alerts/status-pages/list/view.ts:172
• 🟠 Warning · F15 · The hub's status page reads stop at 100 rows and never follow next_cursor · apps/web/src/page/alerts/shared/status-page-commands.ts:21
• 🔵 Note · F10 · The reorder test never renders the optimistic order its title claims · apps/web/src/page/alerts/status-pages/editor/editor.scene.test.ts:144
• 🔵 Note · F11 · pageId(10) and its siblings throw instead of building an id · apps/web/src/page/alerts/status-pages/test-pages.ts:17
• 🔵 Note · F13 · Clearing the address keeps slug blank instead of handing it back to the name · apps/web/src/page/alerts/status-pages/list/update.ts:74
• 🔵 Note · F14 · An empty address shows no error, so Create status page is disabled with no reason · apps/web/src/page/alerts/status-pages/list/view.ts:172
• 🔵 Note · F16 · publishLine renders relative times against the epoch until the clock read lands · apps/web/src/page/alerts/status-pages/editor/view.ts:99
• 🔵 Note · F17 · A blank component name disables Save with nothing saying the name is required · apps/web/src/page/alerts/status-pages/editor/view-components.ts:235
• 🔵 Note · F9 · A failed components read is titled "Couldn't load incidents" · apps/web/src/page/alerts/status-pages/editor/view.ts:161

Production impact

_{d10bce2 · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}