round 1: implement bracket-first manual compaction

docs/cordis-catalog/services.md

@@ -463,6 +463,26 @@ Abstract compaction service. Implementations own trigger policy, retention, and
  */
 abstract compactIfNeeded( agent: CompactAgentContext, trigger: CompactionTrigger, signal: AbortSignal, ): Promise<CompactionResult | null>
 
+/**
+ * Explicitly compact useful history even below automatic pressure thresholds.
+ * Implementations reserve idle turn admission synchronously before any
+ * asynchronous work, select a useful range without writing on a no-op, then
+ * append a standalone `compact/start` before summarization. That durable
+ * marker is the compaction lock until one `compact/end` attempt. Later waking
+ * prompts remain accepted in FIFO order and start only after the optional
+ * durability checkpoint and admission release. Context injected while the
+ * summary runs may sit between the marker pair; only the selected span must
+ * remain stable.
+ *
+ * @param agent - idle agent whose durable history should be compacted.
+ * @param signal - command-owned cancellation forwarded to summarization.
+ * @returns the compaction result, or `null` when no safe useful range exists.
+ * @throws {@link ManualCompactionError} for expected busy, changed-span,
+ * summarization/shrink, commit-stage, or persistence failures, and the exact
+ * abort reason when cancelled. Failed attempts remain visible in the log.
+ */
+abstract compactNow( agent: ManualCompactAgentContext, signal: AbortSignal, ): Promise<CompactionResult | null>
+
 /**
  * Forcibly compact a range of surface nodes into a single summary node.
  * `start` and `end` name an inclusive span by surface position, not numeric seq
@@ -486,7 +506,7 @@ abstract compactRegion( start: number, end: number, agent: CompactAgentContext,
 
 Types: [CompactionResult](../core-data-structures/compaction.md) · [CompactionTrigger](../core-data-structures/compaction.md)
 
-Source: [`packages/compact/compact/src/index.ts:45`](../../packages/compact/compact/src/index.ts)
+Source: [`packages/compact/compact/src/index.ts:76`](../../packages/compact/compact/src/index.ts)
 
 ## `ctx.directoryPicker` — `DirectoryPicker` (abstract seam)