chore(openspec): drop 9 superseded proposals + 11 stub archive files

Drop 9 batch proposals that are superseded by the boocode-lift-analysis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-memory-context-engineering/specs/short-term-context/spec.md

@@ -0,0 +1,65 @@
+## ADDED Requirements
+
+### Requirement: Token budget management
+The system SHALL manage LLM context window limits by tracking token usage and triggering summarization when thresholds are exceeded.
+
+#### Scenario: Token threshold exceeded
+- **WHEN** cumulative message tokens exceed `max_tokens` configuration
+- **THEN** the system SHALL identify messages to summarize starting from oldest
+- **THEN** the system SHALL replace summarized messages with a `RunningSummary` object
+- **THEN** the system SHALL ensure remaining messages + summary fit within `max_tokens` budget
+
+#### Scenario: Partial token budget allocation
+- **WHEN** `max_summary_tokens` is configured (default 256)
+- **THEN** the system SHALL reserve `max_summary_tokens` tokens for the summary itself
+- **THEN** remaining messages SHALL be trimmed to fit within `max_tokens - max_summary_tokens`
+
+### Requirement: Incremental summarization
+The system SHALL support incremental summarization across multiple turns, tracking which messages have already been summarized to avoid redundant work.
+
+#### Scenario: First summarization
+- **WHEN** no existing `RunningSummary` exists and token threshold is exceeded
+- **THEN** the system SHALL call the LLM with an initial summary prompt
+- **THEN** the system SHALL return a `RunningSummary` with `summary`, `summarized_message_ids` set, and `last_summarized_message_id`
+
+#### Scenario: Subsequent summarization (append)
+- **WHEN** a `RunningSummary` exists and new messages exceed threshold
+- **THEN** the system SHALL call the LLM with the existing summary plus new messages
+- **THEN** the system SHALL extend `summarized_message_ids` with newly summarized message IDs
+- **THEN** the system SHALL update `last_summarized_message_id`
+
+### Requirement: Context trimming with summarization hook
+The system SHALL provide a hook that fires before messages are discarded, allowing the daily tier to capture summarized content.
+
+#### Scenario: Pre-trim flush
+- **WHEN** messages are about to be discarded (summarized)
+- **THEN** the system SHALL fire a `memory_flush_hook` with the messages being summarized
+- **THEN** the hook SHALL queue the messages for async memory extraction
+- **THEN** the main thread SHALL NOT block on memory extraction
+
+### Requirement: Token counting with fallback
+The system SHALL provide accurate token counting using `tiktoken` when available, with a char-based fallback.
+
+#### Scenario: tiktoken available
+- **WHEN** tiktoken package is installed
+- **THEN** the system SHALL use `tiktoken.get_encoding("cl100k_base")` for token counting
+- **THEN** token counts SHALL be accurate per OpenAI/Anthropic tokenization
+
+#### Scenario: tiktoken unavailable
+- **WHEN** tiktoken is not installed
+- **THEN** the system SHALL fall back to character-based estimation: `len(text) // 4`
+- **THEN** the system SHALL log a warning about missing tiktoken
+
+### Requirement: Summarization node for LangGraph
+The system SHALL provide a `SummarizationNode` Runnable that integrates into LangGraph state graphs.
+
+#### Scenario: Graph integration
+- **WHEN** `SummarizationNode` is added to a LangGraph workflow
+- **THEN** it SHALL read messages from `input_messages_key` (default "messages")
+- **THEN** it SHALL write updated messages to `output_messages_key` (default "summarized_messages")
+- **THEN** it SHALL store `RunningSummary` in `context.running_summary`
+
+#### Scenario: Equality of input/output keys
+- **WHEN** `input_messages_key` equals `output_messages_key`
+- **THEN** the node SHALL emit a `RemoveMessage(REMOVE_ALL_MESSAGES)` to clear previous state
+- **THEN** the node SHALL write the new message list including the summary