fix(compact): correct _extractText surface-order JSDoc; add disposal to the HMR-safety suite (CBR-005, CBR-006)

Manual review round, two non-blocking findings:

- CBR-005: _extractText's JSDoc claimed it "walks events in log order",
  but it walks the seqs in surface order (the inline comment already said
  so) — the exact distinction CBR-001 paid for, since after a replace a
  high-seq checkpoint heads the surface before lower-seq retained nodes.
  Corrected the JSDoc to match.
- CBR-006: the "HMR safety" suite only asserted registration; the actual
  dispose-and-confirm-cleanup test lived under "llm inject", so a reader
  searching by name could miss it. Added a disposal test to the HMR-safety
  suite (mount via the real plugin fiber with LlmService present so inject
  resolves, dispose, assert ctx.get('compact') is undefined) and reframed
  the llm-inject test's trailing teardown to point at it.

packages/compact/compact-basic/src/index.ts

@@ -601,8 +601,11 @@ export class BasicCompactService extends CompactService {
 
   /**
    * Extract plain-text conversation from a set of surface node seqs, for
-   * feeding into the summarization model. Walks events in log order so the
+   * feeding into the summarization model. Walks the seqs in the order given
-   * summary captures chronological flow.
+   * (surface order, as `compactRegion` slices the surface-node list) so the
+   * summary follows the conversation as the model sees it — which, after a
+   * `replace`, is NOT ascending log-seq order (a high-seq summary node heads the
+   * surface before older retained lower-seq nodes).
    */
   private _extractText(session: Session, seqs: number[]): string {
     const lines: string[] = []

packages/compact/compact-basic/tests/compact-basic.spec.ts

@@ -735,6 +735,21 @@ describe('BasicCompactService HMR safety', () => {
     expect(ctx.compact).toBeDefined()
     expect(ctx.compact).toBeInstanceOf(BasicCompactService)
   })
+
+  it('disposing the plugin fiber unregisters ctx.compact', async () => {
+    // Mount through the real plugin fiber (the Loader path), then dispose it and
+    // confirm the service registration is torn down. LlmService is mounted first
+    // so the service's `inject: ['llm']` resolves and the fiber activates. (The
+    // sibling-fiber ctx.llm resolution this same setup also exercises is covered
+    // under the "llm inject (real plugin-load path)" suite.)
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    const fiber = await ctx.plugin(BasicCompactService, { auto: false })
+    expect(ctx.get('compact')).toBeInstanceOf(BasicCompactService)
+
+    await fiber.dispose()
+    expect(ctx.get('compact')).toBeUndefined()
+  })
 })
 
 describe('BasicCompactService convergence invariant (config)', () => {
@@ -1343,7 +1358,8 @@ describe('BasicCompactService llm inject (real plugin-load path)', () => {
     const result = await svc.compactRegion(session, nodes[0]!.seq, nodes[1]!.seq, 'test-model')
     expect(result.summary).toEqual([{ type: 'text', text: 'CONDENSED' }])
 
-    // HMR: disposing the fiber tears the service registration down.
+    // Tear the fiber down so this test owns no leaked registration; the
+    // dedicated cleanup assertion lives in the "HMR safety" suite.
     await fiber.dispose()
     expect(ctx.get('compact')).toBeUndefined()
   })