test: close per-file coverage gaps opened by the message-machine refactor

Downstream packages lost the tests that exercised their agent-loop-facing
edges when the loop was rewritten. Restore 100% per-file coverage with
behavior tests through public seams: llm-retry config validation and
cancellation races, goal replay drift/staleness/teardown edges, plan-mode
disposed-flush, workspace-context empty-change commits, api-proxy
synchronous send failures, acp-snapshot spill-path extraction and refresh
write-back, ACP injection-triggered turns, cli-demo and tui inbox
lifecycle edges, and agent-loop retry/settlement/lifecycle branches.
The only source changes are narrowly-justified v8 ignore annotations on
invariant guards and one redundant-guard removal (workspace-context).

packages/support/acp-snapshot/tests/normalize.spec.ts

@@ -1,6 +1,7 @@
 import { describe, expect, it } from 'vitest'
 import {
   type NormalizeContext,
+  extractSnapshotSpillPaths,
   normalizeSessionLog,
   normalizeStdout,
   scrubRequestHeaders,
@@ -319,6 +320,24 @@ describe('normalizeSessionLog', () => {
   })
 })
 
+describe('extractSnapshotSpillPaths', () => {
+  it('maps each spill filename to its full matched path, last match wins per name', () => {
+    const log = [
+      'Full formatted result stored at: /tmp/dsh-acp-snapshot-spill/session-c22bc3f1d2af/8a7b6c5d4e3f-bash.txt. Use read with offset/limit, or grep this path to search within it.',
+      'stale copy at /tmp/dsh-acp-snap-012345678/session-aaaaaaaaaaaa/bbbbbbbbbbbb-grep.txt then',
+      'fresh copy at /tmp/dsh-acp-snap-012345678/session-cccccccccccc/dddddddddddd-grep.txt then',
+    ].join('\n')
+    expect(extractSnapshotSpillPaths(log)).toEqual(new Map([
+      ['bash.txt', '/tmp/dsh-acp-snapshot-spill/session-c22bc3f1d2af/8a7b6c5d4e3f-bash.txt'],
+      ['grep.txt', '/tmp/dsh-acp-snap-012345678/session-cccccccccccc/dddddddddddd-grep.txt'],
+    ]))
+  })
+
+  it('returns an empty map when the log carries no snapshot spill paths', () => {
+    expect(extractSnapshotSpillPaths('no spill paths here, only /tmp/other.txt\n')).toEqual(new Map())
+  })
+})
+
 describe('scrubRequestHeaders', () => {
   const headerLine = JSON.stringify({ type: 'session', version: 0, id: 's', createdAt: 1, cwd: '/w' })
   const headerEvent = (header: object) =>

packages/support/acp-snapshot/tests/suite.spec.ts

@@ -455,6 +455,29 @@ describe('refreshFixtureReplacements', () => {
       { from: '/new', to: '/old' },
     ])
   })
+
+  it('stabilizes moved snapshot spill paths by filename while skipping unchanged or unmatched names', () => {
+    const spill = (session: string, hash: string, name: string): string =>
+      `/tmp/dsh-acp-snapshot-spill/session-${session}/${hash}-${name}`
+    const record = (text: string): string =>
+      `${JSON.stringify({ type: 'session', id: 'same', cwd: '/same' })}\n`
+      + `${JSON.stringify({ type: 'tool/result', data: { content: [{ type: 'text', text: `stored at: ${text} ` }] } })}\n`
+    const freshBash = spill('aaaaaaaaaaaa', 'bbbbbbbbbbbb', 'bash.txt')
+    const oldBash = spill('cccccccccccc', 'dddddddddddd', 'bash.txt')
+    const shared = spill('eeeeeeeeeeee', 'ffffffffffff', 'grep.txt')
+    const orphan = spill('111111111111', '222222222222', 'orphan.txt')
+    const logs: HarvestedLog[] = [{
+      id: 'diagnostic',
+      createdAt: 1,
+      content: record(`${freshBash} and ${shared}`),
+    }]
+    const fixtures = [record(`${oldBash} and ${shared} and ${orphan}`)]
+    // bash.txt moved → replaced; grep.txt is identical and orphan.txt has no
+    // fresh counterpart → both skipped.
+    expect(refreshFixtureReplacements(logs, fixtures)).toEqual([
+      { from: freshBash, to: oldBash },
+    ])
+  })
 })
 
 describe('stabilizeRefreshLog', () => {