feat: strategy-view composition — viewFilter, auxiliary merged slots, windowed passthrough (tune-out groundwork)

[Meganeuridae]

What

The context-manager primitives for tune-out (anima-research/agent-framework#77), per the design comment there. Three additions, each inert until configured — zero behavior change for existing callers:

1. ContextManagerConfig.viewFilter — strategy-facing exclusion predicate, applied at the one choke point (strategyMessageView()) through which compile, preview, render-stats, and the tick/onNewMessage StrategyContext all obtain their message view. An excluded message is simply not part of the strategy's world — on both sides of every invariant.

   Why here and nowhere else: exclusion at emission level fails twice — assertFullCoverage judges entries against the whole view and throws on any uncovered message, and select() runs rebuildChunks(store) first, so emission-excluded content still flows into L1 compression (and from there into L2/L3 folds). The view boundary closes both. Excluded messages remain in the store: getMessage/getAllMessages/query are deliberately unfiltered (the tune-out backlog must stay dumpable/auditable).

2. ContextManagerConfig.auxiliaryMessageViews — additional message slots merged read-only into the strategy view, interleaved by chronicle sequence (branch-global across slots — allocated under the store's single write lock — so the merged timeline is deterministic and append-only). Writes still target only the manager's own slot. This is the subconscious's merged (main + own) view from the issue. Freshness across instances comes for free: getAllInternal revalidates against live chronicle state (count + last-item identity) before trusting its cache — pinned by a test.

3. WindowedPassthroughStrategy — passthrough over a sequence-anchored window with coarse re-anchoring: on overflow the anchor jumps forward so the window is ~reAnchorFraction (default 0.5) of usable budget, then stays put until the next overflow. Between jumps, compiled output is a byte-stable prefix + pure appends. A naively sliding front (what PassthroughStrategy.selectFromEnd does) re-busts the KV prefix on nearly every compile — the exact pathology kv-stable folding solves for main agents, and this strategy's consumers get no solver. The anchor persists in a {ns}/windowed:anchor snapshot slot (so it survives restarts and follows branches), and setAnchor() is the external policy hook ("start of the oldest active tune-out").

Compositors are exported standalone (filterMessageStoreView, mergeMessageStoreViews) and unit-tested.

Tests

test/view-composition.test.ts — 9 tests: compositor units (every read surface, cross-view get, sequence interleaving); CM integration (filter excludes from compile but not the store; aux slot merges by sequence; live cross-instance reads after cache priming); windowed strategy (anchor honored + append-stability; overflow re-anchors once and holds through further compiles and modest growth; anchor survives reopen). Full suite: 456 pass / 0 fail.

What this deliberately does not do

No tune-out semantics, no stamping, no subconscious lifecycle — that's the agent-framework half (single PR per antra's preference), which consumes these three primitives plus the ingestion stamp. The viewFilter docstring pins the one contract that half must honor: the predicate must be deterministic per message (ingestion-stamped metadata, not derived state), or prefix stability and strategy bookkeeping suffer.

🤖 Generated with Claude Code

[Meganeuridae]

Per review feedback: converted to draft, stacked on the forthcoming tune-out end-to-end PR in agent-framework — mechanically separable but semantically coupled, so this merges only as part of the full integration review, or not at all. The af PR will link back here; treat the pair as one reviewable unit. (If closing until then is preferred, happy to — nothing here is load-bearing standalone.)

🤖 Generated with Claude Code