H: observerd — autonomous-iteration witness loop (SPEC §2 port)

Port of the load-bearing pieces of mcp-server/observer.ts (Rust
system, 852 lines TS) per SPEC §2's named target. Implements PRD
loop 3 ("Observer loop — watches each run, refines configs").

Routes (all under /v1/observer/* via gateway):
  GET  /observer/health   — liveness
  GET  /observer/stats    — total / successes / failures /
                             by_source / recent_scenario_ops
                             (matches Rust JSON shape exactly)
  POST /observer/event    — record one ObservedOp; auto-defaults
                             timestamp + source, validates required
                             fields (endpoint), persists to JSONL,
                             appends to ring buffer

Architecture:
  - internal/observer/types.go — ObservedOp model + Source taxonomy
    (mcp / scenario / langfuse / overseer_correction). Mirrors the
    Rust shape so JSON round-trips during cutover.
  - internal/observer/store.go — Store + Persistor. Ring buffer cap
    matches Rust's 2000; recent_scenarios cap matches Rust's 10.
    Same persist-then-apply order as pathwayd; same corruption-
    tolerant replay (skip malformed lines + warn).
  - cmd/observerd — :3219 HTTP service, fronted by gateway as
    /v1/observer/*.
  - lakehouse.toml + DefaultConfig — [observerd] block matches the
    pathwayd pattern (Bind + PersistPath; empty path = ephemeral).

Tests + smoke (all PASS):
  - 7 unit tests in store_test.go: validation, default fields,
    stats aggregation, recent-scenarios cap + ordering, ring-buffer
    rollover at cap, JSONL round-trip persistence, corruption-
    tolerant replay (1 valid + 1 corrupt + 1 valid → 2 applied)
  - scripts/observer_smoke.sh: 4 assertions through gateway —
    record 5 events (3 ok / 2 fail across 2 sources), stats
    aggregates correctly, empty-endpoint→400, kill+restart preserves
    via JSONL replay (5 ops, 3 ok, 2 err survive)

Deferred (named in package + cmd doc, not in this commit):
  - POST /observer/review (cloud-LLM hand-review fall-back). The
    heuristic-only path could land cheaply but the productized
    cloud path (qwen3-coder fall-back) is multi-day port.
  - Background loops: analyzeErrors, consolidatePlaybooks,
    tailOverseerCorrections (read overseer_corrections.jsonl into
    the ring buffer once per cycle).
  - escalateFailureClusterToLLMTeam (failure clustering trigger
    that posts to LLM Team's /api/run with code_review mode).

/relevance is NOT duplicated — already ported in 9588bd8 to
internal/matrix/relevance.go (component 3 of SPEC §3.4).

16-smoke regression all green (D1-D6, G1, G1P, G2, storaged_cap,
pathway, matrix, relevance, downgrade, playbook, observer).
13 binaries now: gateway, storaged, catalogd, ingestd, queryd,
vectord, embedd, pathwayd, matrixd, observerd, mcpd, fake_ollama
(plus catalogd-only test build).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cmd/gateway/main.go

@@ -46,6 +46,7 @@ func main() {
 		"embedd_url":   cfg.Gateway.EmbeddURL,
 		"pathwayd_url": cfg.Gateway.PathwaydURL,
 		"matrixd_url":  cfg.Gateway.MatrixdURL,
+		"observerd_url": cfg.Gateway.ObserverdURL,
 	}
 	for k, v := range upstreams {
 		if v == "" {
@@ -67,6 +68,7 @@ func main() {
 	embeddURL := mustParseUpstream("embedd_url", cfg.Gateway.EmbeddURL)
 	pathwaydURL := mustParseUpstream("pathwayd_url", cfg.Gateway.PathwaydURL)
 	matrixdURL := mustParseUpstream("matrixd_url", cfg.Gateway.MatrixdURL)
+	observerdURL := mustParseUpstream("observerd_url", cfg.Gateway.ObserverdURL)
 
 	storagedProxy := gateway.NewProxyHandler(storagedURL)
 	catalogdProxy := gateway.NewProxyHandler(catalogdURL)
@@ -76,6 +78,7 @@ func main() {
 	embeddProxy := gateway.NewProxyHandler(embeddURL)
 	pathwaydProxy := gateway.NewProxyHandler(pathwaydURL)
 	matrixdProxy := gateway.NewProxyHandler(matrixdURL)
+	observerdProxy := gateway.NewProxyHandler(observerdURL)
 
 	if err := shared.Run("gateway", cfg.Gateway.Bind, func(r chi.Router) {
 
@@ -98,6 +101,8 @@ func main() {
 		r.Handle("/v1/pathway/*", pathwaydProxy)
 		// Matrix indexer — /v1/matrix/*  (multi-corpus retrieve+merge per SPEC §3.4)
 		r.Handle("/v1/matrix/*", matrixdProxy)
+		// Observer — /v1/observer/*  (autonomous-iteration witness loop)
+		r.Handle("/v1/observer/*", observerdProxy)
 	}, cfg.Auth); err != nil {
 		slog.Error("server", "err", err)
 		os.Exit(1)