feat: add coordination-ROI band to member Work History

Surfaces "rework saved" at the top of the teammate Work History dialog:
a transparent heuristic over collisions Hermes caught early (eligible =
gitOverlap or critical, with an intervention), credit split across
involved engineers. Shows hard counts (clashes caught, conflict-free
files) plus an info-tooltip breakdown of the estimate.

- shared: optional MemberWorkHistoryRoi field (back-compat, self-zeroes)
- backend: query collisions + interventions in getMemberWorkHistory,
  computeRoi helper
- frontend: RoiBand + RoiTooltip components, hidden when no clashes

Implements docs/plans/work-history-roi.md.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LuV8W8oNYRsDWKoqK8Mkqc

shared/src/index.ts

@@ -56,5 +56,6 @@ export type {
   MemberWorkHistory,
   MemberWorkHistoryEvent,
   MemberWorkHistoryFile,
+  MemberWorkHistoryRoi,
   MemberWorkHistorySource,
 } from './member-history.js';

shared/src/member-history.ts

@@ -33,4 +33,24 @@ export interface MemberWorkHistory {
   };
   files: MemberWorkHistoryFile[];
   timeline: MemberWorkHistoryEvent[];
+  /**
+   * Coordination ROI summary — clashes Hermes caught for this member. Optional
+   * so pods with no collisions / older payloads render without the band.
+   */
+  roi?: MemberWorkHistoryRoi;
+}
+
+export interface MemberWorkHistoryRoi {
+  /** Estimated rework minutes saved (heuristic, labeled "~/est." in UI). */
+  savedMinutes: number;
+  /** Eligible collisions caught early (hard count). */
+  clashesCaught: number;
+  /** Distinct files that hit an eligible clash. */
+  filesDeconflicted: number;
+  /** Member files in flight that never hit a clash. */
+  conflictFreeFiles: number;
+  /** Total member files in flight (git changedFiles). */
+  totalFiles: number;
+  /** Per-kind breakdown for the tooltip. */
+  breakdown: { label: string; count: number; minutesEach: number }[];
 }