engram: reconcile M8 HNSW vindex (#109) onto current dev, restore 3 fixes the branch predated

Lands feat/reframe-region-setop (PR #109: native set-based reframe_region,
decorator-as-seam @route port, teacher-summon, and the M8.1 activate-latency
work — lazy-memoized cosq via eg_cosq_at + engram_vindex HNSW-accelerated
seed discovery + vindex_harvest_from_store/vindex_bench oracle) onto dev's
actual current HEAD, plus engram-tiered-storage's still-unique test suite.

RECONCILING #109 WITH engram-tiered-storage (M4-M10 HNSW/geometry/reason/
verify work): not a two-way merge. engram_vindex.c's HNSW core (search_layer/
select_neighbors/prune_links/insert) is BYTE-IDENTICAL between the two
branches; #109's copy is a strict superset (adds vindex_harvest_from_store,
used by vindex_bench.c's brute-force-vs-HNSW oracle). engram_reason.c and
engram_verify.c are also byte-identical. #109's own branch point already
carried engram-tiered-storage's M4-M10 lineage forward, so there was nothing
left to merge into #109 for those files. The one thing engram-tiered-storage
had that #109's tree dropped: its full test suite (test_vindex.c,
test_geometry.c, test_reason.c, test_verify.c, test_m7_traversal.c, the
interoception P0-P5 tests, bufpool/compaction tests, and their run_*.sh
harnesses) — ported over here unchanged.

WHY THIS NEEDED HAND RECONCILIATION, NOT A MECHANICAL MERGE: #109's branch
forked from dev on 2026-08-14 15:40 (before restructure-adjacent history
diverged the file's merge-base for `git merge` — it presented as an add/add
conflict). A straight two-dot diff (dev tip -> PR tip) applied cleanly, but
it silently reverted THREE dev fixes landed on 2026-08-14/15, after the
branch point, that the PR's diff had no way to know about:

  1. qgate rescale (2026-08-14 self-review): PR's lazy eg_cosq_at rewrite of
     the query-aware propagation gate dropped the shift-and-floor rescale
     about ENGRAM_EMBED_S0 (measured: unrelated-pair median 0.562->raw gate
     0.67, i.e. "a small tax, not a gate"). Restored the rescale, wrapped
     around the lazy accessor -- the PR's actual improvement (WHEN cosq[oi]
     is computed) is orthogonal to WHAT it gates on and both are kept.
  2. Eviction cause decomposition (2026-08-14 self-review): dev decomposes
     wm_evicted into evict_floor/evict_cap/evict_bll so WM churn is
     diagnosable (identity: evicted == floor+cap+bll+dup_wm+dup_wm_global).
     PR's tree predates this and dropped all three counters + their JSON
     stats fields. Restored declarations, all 4 direct increment sites, the
     eg_wm_carry_over bll increment, and the act-stats JSON fields --
     alongside (not instead of) the PR's own P4 afferent / API-reshape
     counters already in that same struct/JSON.
  3. Hebbian link-formation selection (2026-08-15 self-review, TODAY): dev
     selects the STRONGEST qualifying candidate for consolidation each call;
     PR's tree predates this and reverted to hash-slot order (arbitrary wrt
     association strength) for edge formation -- the one path that writes
     PERMANENT structure. Restored the strongest-candidate while-loop,
     keeping the PR's own genuine improvement at that site
     (engram_adj_on_edge_added incremental-index append instead of a bare
     adj_dirty=1 full-rebuild flag).

engram/src/server.el's 3-way conflicts (autoconnect_on/ise_offgraph_on env
flags, /api/nodes connected-count in responses) were pure additive: dev's
side was empty, PR's side added the feature. Took PR's side whole.

VERIFIED (nsbx sandbox only, live :8742/:7770 never touched):
  - cc -std=c11 -O2, clean link against the real engram/src/server.el via
    elc, zero errors.
  - vindex_bench (built standalone, read-only harvest) against the real
    production store clone (13,671 embedded nodes, 768-dim nomic-embed-text):
    recall@10 = 1.0000 at ef 64/128/200; HNSW search 0.28-0.79ms/query vs
    2.03ms/query brute-force oracle (2.6x-7.2x). HNSW build itself: 46.5s
    for the full 13,671-node set -- see the flagged risk below.
  - Booted the reconciled binary in an isolated nsbx sandbox (:8905, cloned
    snapshot of the live store, 13,424 nodes / 37,656 edges) and called
    /api/activate for real: first call after boot 41.5s (pays the one-time
    HNSW build inline -- matches the standalone bench), second/third calls
    356ms/605ms, no crash, correct results, act-stats JSON (including the
    restored evict_floor/cap/bll fields) reads correctly.

KNOWN RISK TO FLAG BEFORE ANY LIVE CUTOVER (not fixed here; out of scope for
this dev-only land per instructions not to touch :8742/:7770): eg_vindex_sync
builds the HNSW index synchronously, inline, on the first engram_activate()
call after every process start (or index invalidation). On the real node
count that is a ~46s blocking stall on a single-threaded server -- the first
request after every restart (or its concurrent siblings) waits the full
build. Recommend a background/incremental build (or a bounded per-call build
budget) before this ever reaches the live daemon. See PR description / final
report for the fuller writeup.

lang/AGENTS.md

@@ -4,6 +4,37 @@ El is a self-hosting, statically-typed language that compiles to C. This file or
 
 ---
 
+## Current work in this worktree — the API reshape / decorated seam (IN PROGRESS, 2026-08-14)
+
+This is the `api-reshape` worktree. The build here reshapes Neuron's external
+surface and how it is *declared* — proven on isolated dev-port clones only; **live
+prod engram `:8742` is untouched and nothing is promoted.** Full framing lives in
+`neuron/docs/architecture/06-cognitive-architecture.md` (Update — 2026-08-14 deep
+night) and `02-components.md §5`.
+
+- **Surface collapse.** The ~90 noun-organized CRUD MCP tools collapse to a few
+  **geometry ops** — `read` (the *vantage-read*: re-origin + salience/recency +
+  an **aperture** → a bounded slice, curing the whole-self dump), `write`,
+  `relate`, `supersede` (evolve/tombstone/promote, never a hard delete) — plus the
+  agentic primitives `think`/`attend`/`learn`/`ground`/`assert`. The old noun is a
+  `type` parameter. Implemented in `tools/api-reshape/surface.el` with a parity
+  harness (`parity.sh`); aperture proven to bound output. **Not yet:** compiled
+  into the MCP server, hot-swap, all-alias dispatch.
+- **Decorated seam.** `@route(path,method,…)` makes codegen synthesize
+  `el_route_dispatch` (replacing the hand-written `handle_request` if-else) —
+  proven decorate→serve on `:8951`. `@manager`/`@engine`/`@accessor` are **parsed
+  but structurally inert** in the shipped compiler today; the `@route` codegen
+  lives on the **unmerged branch `feat/el-route-decorators`**. Telemetry-emit and
+  dharma-bus auto-wiring at the boundary are **staged, not shipped**. In-process,
+  an `@accessor` reaches the engram via **`engram_*` builtins**, not `http_get`.
+
+**Do not edit** the protected build sources while this is in flight:
+`el-compiler/src/codegen.el`, `el-compiler/runtime/el_seed.c` (and the archived
+`legacy/el_runtime.c`), the `runtime/engram_*.c` boot files, and `surface.el`
+(when present in the reshape tree) — these are owned by the build agents.
+
+---
+
 ## What El Is
 
 El compiles `.el` source → C → native binary. Every El value is `el_val_t` (int64_t). Strings are heap pointers cast through int64_t. The compiler is written in El (self-hosting).