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

docs/rfc/implemented/testing/2026-06-11-property-based-testing.md

@@ -8,13 +8,13 @@ Status: implemented (proposed 2026-06-11, accepted 2026-06-14)
 
 ## Context
 
-Example-based tests pin the cases we thought of. The harness's core is protocol-shaped — chunk streams, event logs, schema conversion, inbox scheduling — where the input space is combinatorial and the interesting bugs live in interleavings nobody wrote an example for. The motivating evidence: a `streamBlocks` ordering bug once survived 100% line coverage of the happy paths. Per-file 100% coverage proves every line ran, not that every interleaving is correct.
+Example-based tests pin the cases we thought of. The harness's core is protocol-shaped — chunk streams, event logs, schema conversion, inbox scheduling — where the input space is combinatorial and the interesting bugs live in interleavings nobody wrote an example for. The motivating evidence: a block-assembly ordering bug once survived 100% line coverage of the happy paths. Per-file 100% coverage proves every line ran, not that every interleaving is correct.
 
 ## Decision
 
 Adopt `fast-check` (a root devDependency) with one `tests/properties.spec.ts` per protocol-shaped package, generators tuned for *realistic-but-adversarial* inputs (not uniform noise) and `numRuns` kept so the suite stays well under ~10s locally. Failures print a reproducible seed. (The original proposal also sketched a nightly CI job running 100× the iterations; that was not shipped — the property suite runs only in the normal `push`/`pull_request` CI, and a scheduled high-iteration job remains possible future work.)
 
-- **dsh-llm / BlockAssembler:** arbitrary chunk streams (valid + malformed: duplicate indices, stragglers, missing block-start). Invariants: `flushReady()+flushRemaining() ≡ blocks()` in order; the streamed prefix is always a prefix of final `blocks()`; partial count ≤ distinct indices; re-assembly idempotent.
+- **dsh-llm / BlockAssembler:** arbitrary chunk streams (valid + malformed: duplicate indices, stragglers, missing block-start). Invariants: the blocks `push()` returns incrementally are a prefix of the final `blocks()`, in order; partial count ≤ distinct indices; re-assembly idempotent; streaming and one-shot consumers agree on usage and finish.
 - **dsh-session:** arbitrary event logs. Invariants: `deriveMessages` deterministic; replay-from-seed identical; seq strictly monotonic; non-message events never affect derived history; derived content is decoupled from the log.
 - **dsh-tools:** arbitrary `SchemaSpec`. Invariants: JSON Schema `required` equals the `required:true` keys at every level; conversion total; **and the composition with [runtime arg validation](../architecture/2026-06-11-runtime-arg-validation.md)** — generated args satisfying a spec pass `validateArgs`, and targeted corruptions (dropped required key, non-object top level) are rejected. This closes the validator/`InferArgs` drift risk.
 - **dsh-agent-loop:** arbitrary send schedules against a never-exhausting adapter, driven through the `agent/status` settle signal (no wall-clock sleeps). Invariants: no message lost; turn numbers strictly increase; status transitions stay on the legal machine.