simplify(llm): drop unconsumed adapter-change event and assembled call surfaces

The LLM service exposed three call surfaces (stream/streamBlocks/generate) but
the only production consumer — the agent loop — uses stream() exclusively,
feeding raw chunks through its own BlockAssembler for replay fidelity. Drop the
speculative convenience surfaces and the registry-change event that no listener
consumed, leaving stream() as the single model-call contract for both
production and tests.

- Remove LlmService.streamBlocks() and generate(), the llm/generate waterfall,
  and GenerateResult.
- Remove the llm/adapter-change event (declaration + emits) and the
  listener-throw rollback ordering that existed only to protect it; keep the
  HMR rollback disposer.
- Remove BlockAssembler.flushReady()/flushRemaining()/result() and the flushed
  cursor — the streaming-flush slice existed only for streamBlocks().
- Adapter tests drive a stream()+BlockAssembler helper (tests/assemble.ts)
  instead of generate(), exercising the same path production uses.
- Land the AGENTS.md "RFCs are proposals, not golden truth" principle and move
  both RFCs proposed -> implemented.

Implements:
- docs/rfc/implemented/simplification/2026-06-20-drop-unconsumed-llm-adapter-change-event.md
- docs/rfc/implemented/simplification/2026-06-20-drop-unconsumed-llm-assembled-surfaces.md

packages/core/agent-loop/tests/review-fixes.spec.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'vitest'
 import { Context } from 'cordis'
-import LlmService, { CallId, ContentBlock, MessageSource, StreamChunk } from '@deepseek-ai/dsh-llm'
+import LlmService, { CallId, MessageSource, StreamChunk } from '@deepseek-ai/dsh-llm'
 import SessionStore, { Session, SessionEvent, SessionId, TurnEndReason } from '@deepseek-ai/dsh-session'
 import SystemPrompt from '@deepseek-ai/dsh-system-prompt'
 import ToolRegistry, { defineTool } from '@deepseek-ai/dsh-tools'
@@ -446,90 +446,6 @@ describe('MEDIUM: turn numbering continues across seeded (forked) sessions', ()
   })
 })
 
-describe('LOW: BlockAssembler and streamBlocks edge cases', () => {
-  it('ignores deltas arriving after block-end for the same index (malformed stream)', async () => {
-    const { BlockAssembler } = await import('@deepseek-ai/dsh-llm')
-    const assembler = new BlockAssembler()
-    assembler.push({ type: 'block-start', index: 0, blockType: 'text' })
-    assembler.push({ type: 'text-delta', index: 0, text: 'good' })
-    assembler.push({ type: 'block-end', index: 0, block: { type: 'text', text: 'good' } })
-    assembler.push({ type: 'text-delta', index: 0, text: ' straggler' })
-    expect(assembler.blocks()).toEqual([{ type: 'text', text: 'good' }])
-  })
-
-  it('assembles tool-call blocks from deltas without block-end', async () => {
-    const { BlockAssembler } = await import('@deepseek-ai/dsh-llm')
-    const assembler = new BlockAssembler()
-    assembler.push({ type: 'tool-call-delta', index: 0, id: CallId('c9'), name: 'echo', argumentsDelta: '{"a"' })
-    assembler.push({ type: 'tool-call-delta', index: 0, id: CallId('c9'), argumentsDelta: ':1}' })
-    expect(assembler.blocks()).toEqual([
-      { type: 'tool-call', id: CallId('c9'), name: 'echo', arguments: '{"a":1}' },
-    ])
-  })
-
-  it('streamBlocks flushes delta-only blocks at end of stream (matches generate())', async () => {
-    const ctx = new Context()
-    await ctx.plugin(LlmService)
-    const deltaOnly: StreamChunk[] = [
-      { type: 'text-delta', index: 0, text: 'no ' },
-      { type: 'text-delta', index: 0, text: 'block-end' },
-      { type: 'finish', reason: { kind: 'stop' } },
-    ]
-    ctx.llm.registerAdapter(['m'], new MockAdapter([deltaOnly, deltaOnly]))
-
-    const blocks: ContentBlock[] = []
-    for await (const block of ctx.llm.streamBlocks({ model: 'm', messages: [] })) blocks.push(block)
-    expect(blocks).toEqual([{ type: 'text', text: 'no block-end' }])
-
-    const generated = await ctx.llm.generate({ model: 'm', messages: [] })
-    expect(generated.message.content).toEqual(blocks)
-  })
-
-  it('streamBlocks preserves stream order when an open block precedes a closed one', async () => {
-    const ctx = new Context()
-    await ctx.plugin(LlmService)
-    // index 0 never gets block-end (delta-only); index 1 closes mid-stream.
-    const interleaved: StreamChunk[] = [
-      { type: 'text-delta', index: 0, text: 'first, open' },
-      { type: 'block-start', index: 1, blockType: 'text' },
-      { type: 'text-delta', index: 1, text: 'second, closed' },
-      { type: 'block-end', index: 1, block: { type: 'text', text: 'second, closed' } },
-      { type: 'finish', reason: { kind: 'stop' } },
-    ]
-    ctx.llm.registerAdapter(['m'], new MockAdapter([interleaved, interleaved]))
-
-    const blocks: ContentBlock[] = []
-    for await (const block of ctx.llm.streamBlocks({ model: 'm', messages: [] })) blocks.push(block)
-    expect(blocks).toEqual([
-      { type: 'text', text: 'first, open' },
-      { type: 'text', text: 'second, closed' },
-    ])
-
-    // identical to generate()'s assembled order
-    const generated = await ctx.llm.generate({ model: 'm', messages: [] })
-    expect(generated.message.content).toEqual(blocks)
-  })
-
-  it('streamBlocks yields closed blocks incrementally once preceding blocks close', async () => {
-    const ctx = new Context()
-    await ctx.plugin(LlmService)
-    const script: StreamChunk[] = [
-      { type: 'block-start', index: 0, blockType: 'text' },
-      { type: 'text-delta', index: 0, text: 'a' },
-      { type: 'block-end', index: 0, block: { type: 'text', text: 'a' } },
-      { type: 'block-start', index: 1, blockType: 'text' },
-      { type: 'text-delta', index: 1, text: 'b' },
-      { type: 'block-end', index: 1, block: { type: 'text', text: 'b' } },
-      { type: 'finish', reason: { kind: 'stop' } },
-    ]
-    ctx.llm.registerAdapter(['m'], new MockAdapter([script]))
-
-    const blocks: ContentBlock[] = []
-    for await (const block of ctx.llm.streamBlocks({ model: 'm', messages: [] })) blocks.push(block)
-    expect(blocks).toEqual([{ type: 'text', text: 'a' }, { type: 'text', text: 'b' }])
-  })
-})
-
 describe('LOW: discriminated SessionEvent narrows without casts', () => {
   it('narrows event.data from event.type', () => {
     const session = new Session(SessionId('s'))