briefings: add search-on-sx loop briefing

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plans/agent-briefings/search-loop.md

@@ -0,0 +1,110 @@
+# search-on-sx loop agent (single agent, queue-driven)
+
+Role: iterates `plans/search-on-sx.md` forever. **Full-text + structured search on
+Haskell** — tokenize, inverted index, query AST, boolean + phrase + ranked
+queries (TF-IDF / BM25), ACL-aware post-filter, federated index merge. Typed ADTs
+make query parsing clean; lazy lists make posting-list iteration efficient. Sits on
+`lib/haskell/` (1514/1514 already green); adds a search-shaped vocabulary on top.
+
+```
+description: search-on-sx queue loop
+subagent_type: general-purpose
+run_in_background: true
+isolation: worktree
+```
+
+## Prompt
+
+You are the sole background agent working `plans/search-on-sx.md`. Isolated
+worktree `/root/rose-ash-loops/search` on branch `loops/search`, forever, one
+commit per feature. Push to `origin/loops/search` after every commit. Never touch
+`main` or `architecture`.
+
+## Restart baseline — check before iterating
+
+1. Read `plans/search-on-sx.md` — roadmap + Progress log.
+2. `ls lib/search/` — pick up from the most advanced file.
+3. If `lib/search/tests/*.sx` exist, run them via `bash lib/search/conformance.sh`.
+   Green before new work.
+4. If `lib/search/scoreboard.md` exists, that's your baseline.
+5. Read the `lib/haskell/` public API once — that's your substrate. `lib/haskell/
+   haskell.sx` exists; also study `runtime.sx`, `eval.sx`, `parser.sx`, `infer.sx`,
+   `match.sx`, `map.sx`, `set.sx`, `testlib.sx`. Learn how to declare ADTs, pattern
+   match, and use the `Map`/`Set` helpers before writing index code. Verify the real
+   exported names with sx_find_all / grep — don't assume from the plan's sketch.
+
+## The queue
+
+Phase order per `plans/search-on-sx.md`:
+
+- **Phase 1** — tokenize + inverted index + simple term lookup
+  (`Map Term [(DocId,[Pos])]`, insert/lookup, `(search/index doc)`,
+  `(search/query term)`).
+- **Phase 2** — query AST + boolean/phrase eval (Term | And | Or | Not | Phrase;
+  posting-list set ops; positional phrase match).
+- **Phase 3** — ranking (TF-IDF, BM25), top-N.
+- **Phase 4** — ACL-aware post-filter + federation (merge per-peer indices).
+
+Within a phase, pick the checkbox that unlocks the most tests per effort.
+
+Every iteration: implement → test → commit → tick `[ ]` → Progress log → next.
+
+## Ground rules (hard)
+
+- **Scope:** only `lib/search/**` and `plans/search-on-sx.md`. Do **not** edit
+  `spec/`, `hosts/`, `shared/`, other `lib/<lang>/` dirs, `lib/stdlib.sx`, or
+  `lib/` root. May **import** from `lib/haskell/` only (its public API). Do **not**
+  modify Haskell.
+- **NEVER call `sx_build`.** 600s watchdog. If the sx_server binary is broken →
+  Blockers entry, stop. Run tests by invoking the sx_server binary directly from a
+  conformance.sh (model it on `lib/haskell/conformance.sh`), pointing `SX_SERVER`
+  at `/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe` — fresh
+  worktrees have no `_build/`, so the relative path won't resolve.
+- **Shared-file issues** → plan's Blockers with minimal repro; don't fix here.
+- **SX files:** `sx-tree` MCP tools ONLY. **They take `file:` not `path:`** — a
+  wrong key yields `Yojson Type_error("Expected string, got null")`, which looks
+  like a broken binary but is just a param mismatch. `sx_validate` after edits.
+  Path-based edits (`sx_replace_node`) count comment headers in their indices and
+  can clobber the wrong node — re-read after, or prefer `sx_write_file` for small
+  files.
+- **Unicode in `.sx`:** raw UTF-8 only, never `\uXXXX` escapes.
+- **Commit granularity:** one feature per commit. Short factual messages
+  (`search: phrase query positional match + 7 tests`). Push to `origin/loops/search`.
+- **Plan file:** update Progress log (newest first) + tick boxes every commit.
+
+## search-specific gotchas
+
+- **Posting lists are the hot path.** Keep them sorted by DocId so boolean AND/OR
+  are linear merges, not nested scans. Phrase match needs positions, so store
+  `(DocId, [Pos])` — don't drop positions early to save space; you can't recover them.
+- **Tokenization decides recall.** Normalize consistently (lowercase, strip
+  punctuation) on BOTH index and query side, or queries silently miss. Test the
+  index/query symmetry explicitly.
+- **Ranking must be deterministic on ties.** TF-IDF/BM25 scores collide; always
+  add a stable tiebreak (DocId ascending) or tests flake.
+- **ACL filter is per-viewer and post-ranking.** Filter the result list against the
+  viewer, after scoring — never bake visibility into the index (the same index
+  serves all viewers). Inject the permit predicate; don't hardwire an ACL module
+  that doesn't exist yet.
+- **Federation merges indices, not results.** Merging per-peer inverted indices
+  (union posting lists per term) is cleaner and rank-correct vs merging ranked
+  result lists. Mock peer indices in tests.
+
+## General gotchas (all loops)
+
+- SX `do` = R7RS iteration. Use `begin` for multi-expr sequences.
+- `cond`/`when`/`let` clauses evaluate only the last expr — wrap multiples in `begin`.
+- `let` is parallel, not sequential — nest `let`s when a binding references an earlier one.
+- `env-bind!` creates a binding; `env-set!` mutates an existing one (walks scope chain).
+- `sx_validate` after every structural edit.
+- Namespace-prefix all guest helpers (`search/...`) — short/host-colliding names
+  get silently shadowed or hang the runtime.
+
+## Style
+
+- No comments in `.sx` unless non-obvious.
+- No new planning docs — update `plans/search-on-sx.md` inline.
+- Short, factual commit messages.
+- One feature per iteration. Commit. Log. Push. Next.
+
+Go. Start by reading the plan; find the first unchecked `[ ]`; implement it.