apply_changes: unify the mutation tool with assign + milestone (#24)

The write path handled only the est/* and p/* label axes. Extend it to the two
mutations dogfooding proved were missing — assignee and milestone — behind one
unified change model:

- IssueChange gains `assign` and `remilestone` kinds. `planIssueChange` is now
  typed to LabelChange (the label kinds only); `isLabelChange` narrows, and a new
  pure `summarizeChange(change, currentLabels?)` gives one confirm line for ANY
  kind (label kinds delegate to describeChange; field writes describe directly).
- GiteaClient gains `setIssueAssignees` / `setIssueMilestone` (PATCH /issues/{n},
  returning the updated issue; milestone 0 clears).
- The main `gitea:applyChange` handler branches: label swaps resolve ids +
  setIssueLabels as before; field writes call the new client methods. Snapshot
  invalidated either way so board + forecast catch up. ApplyChangeResult.plan is
  now optional (absent for field writes).
- issue-screen uses summarizeChange for its diff preview.

Tests: +5 covering isLabelChange, and summarizeChange for assign/unassign,
milestone set-by-title / by-id / removal, and label delegation. Full core suite
132 green; core + desktop typecheck clean.

Follow-up (rest of #24): surface assignee/milestone pickers in the Adjust dialog
and extend the agent's propose_change tool so Reginald can propose them too.

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

apps/desktop/src/main/gitea.ts

@@ -19,6 +19,7 @@ import {
   type GiteaConfig,
   type GiteaLabel,
   type IssueChange,
+  isLabelChange,
   type LifecycleEvent,
   makeDirectiveEntry,
   parseCapacityConfig,
@@ -263,19 +264,32 @@ export function registerGiteaIpc(): void {
     return client.getIssue(index)
   })
 
-  // The write path (apply_changes). Additive label swaps, applied only after the
-  // renderer's propose-approve. Returns the plan + the freshly-read issue.
+  // The write path (apply_changes), applied only after the renderer's propose-
+  // approve. Label swaps (est/p) return the plan; field writes (assign, milestone)
+  // return the freshly-read issue directly. Either way the snapshot is invalidated
+  // so the board + forecast reflect the change.
   ipcMain.handle('gitea:applyChange', async (_event, change: IssueChange) => {
     const client = getGiteaClient()
     if (!client) return { ok: false as const, reason: 'unconfigured' as const }
-    const current = await client.getIssue(change.issue)
-    const plan = planIssueChange(current.labels, change)
-    if (plan.noop) return { ok: true as const, plan, issue: current }
-    const ids = await resolveLabelIds(client, plan.labels)
-    await client.setIssueLabels(change.issue, ids)
-    const issue = await client.getIssue(change.issue)
-    invalidateSnapshot() // the board + forecast must reflect the label change
-    return { ok: true as const, plan, issue }
+
+    if (isLabelChange(change)) {
+      const current = await client.getIssue(change.issue)
+      const plan = planIssueChange(current.labels, change)
+      if (plan.noop) return { ok: true as const, plan, issue: current }
+      const ids = await resolveLabelIds(client, plan.labels)
+      await client.setIssueLabels(change.issue, ids)
+      const issue = await client.getIssue(change.issue)
+      invalidateSnapshot()
+      return { ok: true as const, plan, issue }
+    }
+
+    // Field writes — the client returns the updated issue.
+    const issue =
+      change.kind === 'assign'
+        ? await client.setIssueAssignees(change.issue, change.assignee ? [change.assignee] : [])
+        : await client.setIssueMilestone(change.issue, change.milestone)
+    invalidateSnapshot()
+    return { ok: true as const, issue }
   })
 
   // capture_work filing: open each approved issue with its est/* + p/* labels.

apps/desktop/src/renderer/src/components/screens/issue-screen.tsx

@@ -2,13 +2,12 @@
 import React, { useState } from 'react'
 
 import {
-  describeChange,
   type EstimateLabel,
   ESTIMATE_LABELS,
   type IssueChange,
-  planIssueChange,
   type PriorityLabel,
   PRIORITY_LABELS,
+  summarizeChange,
 } from '@commitea/core'
 
 import { ISSUE_DETAIL, type IssueDetail, type IssueRef } from '../../data/fixtures.js'
@@ -78,7 +77,7 @@ export function IssueScreen({
   if (priority !== curPriority)
     pendingChanges.push({ kind: 'reprioritize', issue: issue.id, priority: (priority || null) as PriorityLabel | null })
 
-  const diffs = pendingChanges.map((c) => describeChange(planIssueChange(labels, c)))
+  const diffs = pendingChanges.map((c) => summarizeChange(c, labels))
 
   const apply = async () => {
     if (!onApplyChange || pendingChanges.length === 0) return

apps/desktop/src/renderer/src/global.d.ts

@@ -17,7 +17,8 @@ import type {
 /** The result of a write through the bridge. */
 export type ApplyChangeResult =
   | { ok: false; reason: 'unconfigured' }
-  | { ok: true; plan: LabelPlan; issue: GiteaIssue }
+  // `plan` is present for label swaps (est/p); absent for field writes (assign, milestone).
+  | { ok: true; plan?: LabelPlan; issue: GiteaIssue }
 
 /** The result of filing captured issues. */
 export type CreateIssuesResult =