feat(#221,#229): Timeline scale/year view, allocation editing, CSV TemplateSize, Gantt UX polish

[NickMonrad]

Summary

Closes #221 (Timeline scale toggle) and #229 (CSV TemplateSize). Also ships a large set of Timeline UX improvements made during the same session.

Related issues

Closes #221
Closes #229

Changes

Core issues

• Timeline scale toggle (Wk / Mo / Qtr / Yr) — new Year scale shows H1/H2 top row and Q1–Q4 bottom row at 8 px/week, suitable for 2+ year projects
• TemplateSize column in backlog CSV — importing a row with TemplateSize=S (XS/S/M/L/XL) auto-expands linked template tasks using that tier's hours
• Cross-epic FeatureDependsOn in CSV import — qualified format EpicName::FeatureName resolves dependencies across epic boundaries

Timeline UX

• Allocation mode editing in Resource Counts panel — set each named resource to T&M / Full Project / Timeline, with % allocation field
• Timeline start/end weeks — appear for named resources in Timeline mode (W[start] – W[end] inputs)
• Expand All / Collapse All toggle in Gantt label panel header
• Dependency picker search filter — type to filter the epic dep dropdown
• Top mirror scrollbar — synced horizontal scrollbar above the Gantt so you can scroll without reaching the bottom
• Full-width Gantt layout — removes the empty left/right margins; chart uses the full browser width
• Two-line epic labels — longer epic names wrap to a second line instead of truncating

Bug fixes

• Onboarding/buffer zone calc — computeDates() now applies onboardingWeeks offset so tooltip dates and zone positions are correct at all scales
• Adaptive zone labels — zone text shortens at compressed scales (Onboarding → Onbrd → O) to fit within the zone rect
• Label width alignment — LABEL_W=380 now consistently applied to ResourceHistogram and NamedResourcesPanel (was hardcoded 300, causing misalignment)
• Histogram bars at year scale — bar inset is now proportional to colW (min 1px, max 4px) instead of hardcoded 8px which produced zero-width bars at year scale
• Auto-reschedule on resource changes — scheduler only auto-fires on first run (entries.length === 0); resource mutations set a stale banner instead
• Expand state reset on timeline refetch — uses knownEpicIds ref (tracks all ever-seen epic IDs) so collapsing all is preserved across mutations. Previous fix using expandedEpics.size === 0 check failed because Collapse All empties the set, making all epics look new
• Named resource T&M histogram per-person — T&M bars divided by the number of named resources in the pool so each person shows their share (e.g. 2 engineers → 5/5 days each, not 10/10)
• PNG export width — respects active scale's colW (was always using week-scale width)
• Top scrollbar width — synced to actual Gantt content width at current scale

E2E Tests

No new E2E tests in this PR — the existing timeline and backlog specs cover the core flows. Scale toggle and CSV TemplateSize are covered by manual verification.

Tests added/modified: none

E2E test results: existing suite unmodified; server tests 142/142 ✅

Testing

• npm test passes in /server (142 tests)
• npx tsc --noEmit passes in /server
• npx tsc --noEmit passes in /client
• npm run test:e2e — not run (no new Playwright tests added)
• e2e/TESTS.md — no changes needed

Notes

• The knownEpicIds ref approach is the correct fix for the expand/collapse reset bug. An earlier attempt using epicInitDone ref still failed because the merge logic compared against expandedEpics (empty after collapse) not against the set of known IDs.
• Year scale at 8 px/week means a 2-year project renders at ~832 px, fitting comfortably in a 1440 px viewport.
• Named resource allocation changes (mode/%) do not auto-reschedule — they set the stale banner. This is intentional.