Per-incident permalink pages for feed item links

[amondnet]

Context

Incident RSS/Atom feeds landed in #(this branch: amondnet/feed, commit 7f43ea5) — /feed.rss, /feed.atom, and the Statuspage-style /history.rss, /history.atom aliases, generated by @statusbeam/core's buildRssFeed/buildAtomFeed.

One deliberate shortcut: because there is no dedicated per-incident page yet, every feed item/entry links to the status-page root (/) rather than a real incident permalink:

• RSS <item><link> → ${siteUrl}/
• Atom <entry><link rel="alternate"> → ${siteUrl}/

Entry uniqueness is preserved via tag: URIs (tag:<host>,2005:Incident/<id>), so readers still de-dupe correctly — but the links aren't deep links.

This mirrors how Statuspage.io/incident.io link each entry to /incidents/<id>.

Proposal

Add per-incident permalink pages and point the feed (and the on-page incident cards) at them.

• A route like /incidents/[id] (or /incidents/[slug]) rendering a single incident's timeline
• Update buildRssFeed/buildAtomFeed item/entry links to the incident permalink instead of /
• Anchor/link the incident cards in IncidentList to their permalink
• Decide locale strategy for incident pages (feeds are currently English-only, single canonical document)

Out of scope / open questions

• Locale-aware feeds — feeds are English-only right now. If we want /{locale}/feed.atom, that's a separate decision (most status providers keep one canonical, language-neutral feed).
• Incident permalink identifier: numeric id vs. a stable slug.

Pointers

• Generator + link construction: packages/core/src/feed.ts
• Endpoints: apps/web/src/pages/{feed,history}.{rss,atom}.ts, shared handler apps/web/src/lib/feed.ts
• Incident model + helpers: packages/core/src/incidents.ts
• On-page rendering: apps/web/src/components/IncidentList.tsx