feat: capacity-aware scheduling (#8) — real focus factors drive every forecast

Turns the single-serial-worker scheduler into a capacity-aware, multi-lane one.
Configured team members become lanes; an issue runs on its assignee's lane (or the
earliest-free lane), its duration scaled by that lane's throughput
(focusFactor × allocation). Every forecast — Focus cone, Runway, milestone
drill-in — is now capacity-aware.

core (@commitea/core):
- capacity/capacity-v0: CapacityMember + capacityPerWorkday + parseCapacityConfig
  (clamps, drops invalid; degrades to []).
- scheduler/scheduler-capacity-v0: scheduleWithCapacity reuses the v0 topo order +
  critical path, re-lays work across lanes (layoutOnLanes, resolveLanes, makespan).
  Empty workers → the single serial plan verbatim.
- forecast() gains options.workers: each MC trial lays sampled durations across the
  lanes and takes the makespan; serial path unchanged. SchedulableIssue gains
  assignee; ScheduledItem gains worker.
- 11 new tests (parse/clamp, parallelism halves makespan, speed scaling, assignee
  routing, cross-lane deps, forecast makespan shrinks with lanes).

app:
- pm-state capacity/members.json read (readCapacity + pmstate:capacity bridge);
  useCapacity hook → workers; forecastBacklog/runwayView/milestoneView pass workers.
- Runway Capacity card shows the real config (person · focus · alloc · pd/day).

Config lives in pm-state (D4); seeded christian(0.8)/stephen(0.6×0.5). Degrades to
the fixture/serial when absent.

Verified: 128 core tests green, desktop typecheck clean, 14 fixture e2e green. Live:
the capacity card is real, and the P2 forecast shifts 32d→37d — honest, since real
focus factors (<1) replace the v0 focus-1.0 assumption.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/core/src/scheduler/scheduler-v0.ts

@@ -21,6 +21,8 @@ export interface SchedulableIssue {
   estimateDays: number | null
   /** 1 (most urgent) … 4; null when unset. */
   priority: number | null
+  /** gitea assignee login, for capacity-aware lane routing; optional. */
+  assignee?: string | null
 }
 
 export interface DependencyEdge {
@@ -45,6 +47,8 @@ export interface ScheduledItem {
   /** On a longest-duration dependency chain. */
   critical: boolean
   rationale: string
+  /** Lane it's scheduled on, when capacity-aware; absent for the single-worker plan. */
+  worker?: string
 }
 
 export interface SchedulePlan {