fix(workspace-context): restore the no-unrepresented-commit gate after master merge

The master merge rewrote reconcileInstructionContext and dropped this
branch's gate: when no transition survives rendering (tiny budgets
produce notice-only text), emit nothing and commit nothing so the next
pass retries. Restore it, align the inbox one-byte test with that
contract (an unrepresentable change is held back, not committed at 1
byte), and move the nested-retry test's probe assertions to sync time
where reconciliation now runs. Also restore master's markdown spec
casts lost in an earlier merge.

packages/client/ui-primitives/tests/markdown.spec.tsx

@@ -162,7 +162,7 @@ describe('MarkdownText', () => {
     expect(() => tokenizer?.call({
       parser: { constructs: { attentionMarkers: {} } },
       previous: null,
-    }, {}, () => undefined, () => undefined)).toThrow(
+    } as never, {} as never, () => undefined, () => undefined)).toThrow(
       'micromark CommonMark attention markers are unavailable',
     )
   })

packages/context/workspace-context/src/state.ts

@@ -405,6 +405,10 @@ export async function reconcileInstructionContext(
   }
   if (items.length === 0) return undefined
   const rendered = renderInstructionChanges(items, resolved.maxBytes)
+  // When no transition survived rendering (tiny budgets render notice-only
+  // text), emit nothing and commit nothing — the uncommitted versions make the
+  // next pass retry instead of spamming notice-only contexts.
+  if (rendered.text.length === 0 || rendered.changes.length === 0) return undefined
   return {
     context: workspaceContextHook(rendered.text, rendered.changes),
     versionUpdates: retainedInstructionVersionUpdates(versionUpdates, rendered.changes),

packages/context/workspace-context/tests/workspace-context.spec.ts

@@ -3815,13 +3815,18 @@ describe('dynamic nested workspace context injection', () => {
         signal: testToolSignal,
         callId: CallId('read-tiny-budget-1'), name: 'read', arguments: { file_path: join('pkg', 'file.txt') }, agent,
       })
+      await syncWorkspaceContext(ctx, agent)
       const second = await ctx.tools.execute({
         signal: testToolSignal,
         callId: CallId('read-tiny-budget-2'), name: 'read', arguments: { file_path: join('pkg', 'file.txt') }, agent,
       })
+      await syncWorkspaceContext(ctx, agent)
 
       expect(first.additionalContexts).toBeUndefined()
       expect(second.additionalContexts).toBeUndefined()
+      // Nothing was emitted, and the uncommitted version made the second sync
+      // probe the instruction file again — the retry.
+      expect(agent.inbox.nextStep).toHaveLength(0)
       expect(fs.readTargets.filter(path => path === instructionPath)).toHaveLength(2)
     } finally {
       await ctx.fiber.dispose()
@@ -3916,7 +3921,7 @@ describe('workspace context inbox synchronization', () => {
     }
   })
 
-  it('keeps a dynamic change within a one-byte positive render budget', async () => {
+  it('holds back a dynamic change a one-byte positive render budget cannot represent', async () => {
     const root = await tempRepo()
     const home = await tempRepo()
     const ctx = new Context()
@@ -3934,8 +3939,10 @@ describe('workspace context inbox synchronization', () => {
 
       await syncWorkspaceContext(ctx, agent)
 
-      expect(agent.inbox.nextStep).toHaveLength(1)
-      expect(Buffer.byteLength(blocksText(agent.inbox.nextStep[0]?.content), 'utf8')).toBeLessThanOrEqual(1)
+      // One byte cannot semantically represent the transition, so nothing is
+      // emitted and nothing commits — the uncommitted version retries on the
+      // next touch instead of committing state the model never saw.
+      expect(agent.inbox.nextStep).toHaveLength(0)
     } finally {
       await ctx.fiber.dispose()
       await rm(root, { recursive: true, force: true })