chore(openspec): drop 9 superseded proposals + 11 stub archive files

Drop 9 batch proposals that are superseded by the boocode-lift-analysis
(boocontext-audit, conductor upgrades, self-healing/verify-gate skills):
add-3tier-memory, import-llm-evaluator, import-pregel-engine, plugin-platform,
conductor-evolution, code-intelligence-upgrade, dev-workflow, ui-overhaul,
agent-reliability.

Delete 11 stub archive files (49-66B each, 'Status: Shipped. Archived.' only)
that provide zero documentation value over the existing CHANGELOG.md + git tags.

openspec/changes/archived/2026-06-07-eval-sandbox-agent-runtime/specs/state-graph/spec.md

@@ -0,0 +1,43 @@
+## ADDED Requirements
+
+### Requirement: State definition via annotations
+
+The system SHALL provide an `Annotation` API for defining graph state schemas:
+
+- `Annotation<T>(reducer?)` — creates a state key with optional reducer
+- `Annotation.Root({ key: Annotation<T> })` — combines keys into a state schema
+- Reducers: `LastValue` (default — overwrite), `BinaryOperator` (custom merge function)
+
+#### Scenario: Annotation.Root defines typed state
+
+- **WHEN** `const State = Annotation.Root({ messages: Annotation<string[]>(addMessages), step: Annotation<number>() })` is defined
+- **THEN** `State` SHALL have `State`, `Update`, and `Node` type members
+
+#### Scenario: LastValue reducer replaces on each write
+
+- **WHEN** a node writes `{ step: 2 }` and then `{ step: 3 }` in the same step
+- **THEN** the LastValue channel SHALL throw an `InvalidUpdateError`
+
+#### Scenario: BinaryOperator reducer accumulates
+
+- **WHEN** a node returns `{ messages: ["hello"] }` and another returns `{ messages: ["world"] }` with an `addMessages` reducer
+- **THEN** the final state SHALL contain `messages: ["hello", "world"]`
+
+### Requirement: StateGraph builder
+
+The system SHALL provide a `StateGraph` class for constructing stateful agent graphs.
+
+#### Scenario: StateGraph is constructed with state schema
+
+- **WHEN** `new StateGraph({ stateSchema: State })` is called
+- **THEN** the graph SHALL accept nodes that receive and can update the defined state
+
+#### Scenario: Nodes can read and write state
+
+- **WHEN** a node function receives state with `{ messages, step }` and returns `{ step: step + 1 }`
+- **THEN** the graph SHALL update `step` and preserve `messages`
+
+#### Scenario: Conditional edges route based on state
+
+- **WHEN** `addConditionalEdges("node_a", (state) => state.step > 5 ? "end" : "node_b")` is added
+- **THEN** execution SHALL route based on the state value at runtime