feat(client): widget "what's new" changelog popup (#31)

[MateuszPaulski]

Adds the in-widget "what's new" release-highlights popup from the approved spec (v2) on #31.

What changed

• New packages/client/src/whatsnew/ slice
  • highlights.ts — hand-curated, newest-first HIGHLIGHTS content file (the first entry's version doubles as the "latest announced version"; no build-time version constant).
  • version.ts — pure helpers: numeric-tuple compareVersions (so 0.9.1 < 0.10.0), entriesNewerThan, latestVersion.
  • storage.ts — whatsNewSeenSetting: SettingEntry<string | null> (on-disk key airside:whats-new-seen), registered in the client settings store per ADR-0046/0047 — no hand-rolled localStorage access.
  • WhatsNewModal.tsx — presentational Radix dialog mirroring IdentityModal (portal container, air: tokens, shared Button, "Got it" dismiss).
  • WhatsNewProvider.tsx — owns the auto-show-once-per-version flow, gated on identity-present: null last-seen seeds silently (no popup for brand-new reviewers), older last-seen opens with every newer entry, newest first, dismissal persists the latest version. Exposes useWhatsNew() for manual re-open (single latest entry).
• Wiring — WhatsNewProvider mounts inside IdentityProvider in app.tsx; a ✦ ghost icon button (aria-label="What's new") joins the panel-list header next to the close button.
• Settings store — one-line whatsNewSeen registration in ENTRIES; the generic store.test.ts suite (read-once count, defaults, round-trip, malformed-JSON, wrong-type) now covers the new key.
• Tests — 22 new: version helpers, HIGHLIGHTS invariants (non-empty, unique strictly-descending versions, well-formed entries), modal rendering/dismiss, and provider auto-show/seed/persist/once-only/identity-gate behaviour (each case seeds localStorage then resetSettings() per the ADR-0046 read-once rule).
• Docs — RELEASING.md gains the "prepend a HIGHLIGHTS entry when cutting a user-facing release" step, with a pointer from CLAUDE.md's Changesets section.
• Changeset — @airnauts/airside-client patch.

Verification

• pnpm lint (biome ci) — exit 0.
• pnpm --filter @airnauts/airside-client test — 58 files, 405 tests passed.
• pnpm --filter @airnauts/airside-client build — tsup + tsc --build --force green.

Closes #31

🤖 Draft opened by airside-agent — automated build of #31.

[MateuszPaulski]

🤖 airside-agent review — 260e134 · 3 finding(s)

Sev	Location	Finding
🟠 high	packages/client/src/app/app.tsx:89	PR is unmergeable — conflicts with origin/main in 4 files (icon-set unification, branding footer landed since merge-base)
🟡 medium	packages/client/src/panel/PanelListView.tsx:60	Raw ✦ glyph bypasses main's single-icon-definition-point convention — use a ui/icons SparkleIcon
⚪ low	packages/client/src/whatsnew/version.ts:17	compareVersions returns NaN for non-numeric segments — silently suppresses auto-show

Implementation is spec-faithful and well-tested (settings-store persistence, identity-gated once-per-version auto-show, patch changeset). The high (merge main + re-apply onto updated files) is being auto-fixed.

[MateuszPaulski]

🤖 airside-agent review — 74d4e19 · ✅ review clean (0 findings). Prior high (merge conflicts), medium (raw ✦ → SparkleIcon), and low (validate regex) all verified resolved. Note: the e2e check failed on runner infrastructure (apt 403 installing Playwright, no tests executed) — re-running it; ci job passed.