briefings: add mod-on-sx loop briefing

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

plans/agent-briefings/mod-loop.md

@@ -0,0 +1,109 @@
+# mod-on-sx loop agent (single agent, queue-driven)
+
+Role: iterates `plans/mod-on-sx.md` forever. **Moderation on Prolog** — reports,
+policy rules, decisions as backtracking proof search, audit trails, escalation
+state machine, federation. Where acl-sx asks "may this happen?", mod-sx asks
+"should this stay?" Sits on `lib/prolog/` (its test suite already green); adds a
+moderation-shaped vocabulary on top.
+
+```
+description: mod-on-sx queue loop
+subagent_type: general-purpose
+run_in_background: true
+isolation: worktree
+```
+
+## Prompt
+
+You are the sole background agent working `plans/mod-on-sx.md`. Isolated worktree
+`/root/rose-ash-loops/mod` on branch `loops/mod`, forever, one commit per feature.
+Push to `origin/loops/mod` after every commit. Never touch `main` or `architecture`.
+
+## Restart baseline — check before iterating
+
+1. Read `plans/mod-on-sx.md` — roadmap + Progress log.
+2. `ls lib/mod/` — pick up from the most advanced file.
+3. If `lib/mod/tests/*.sx` exist, run them via `bash lib/mod/conformance.sh`. Green
+   before new work.
+4. If `lib/mod/scoreboard.md` exists, that's your baseline.
+5. Read the `lib/prolog/` public API once — that's your substrate. The plan cites
+   `lib/prolog/prolog.sx` but that file does **not** exist; the real entry points
+   are `lib/prolog/runtime.sx`, `query.sx`, `compiler.sx`, `parser.sx`. Investigate
+   them (sx_find_all / grep for `(define ` heads) to learn how to assert facts and
+   run queries before writing any policy code.
+
+## The queue
+
+Phase order per `plans/mod-on-sx.md`:
+
+- **Phase 1** — report representation + simple policy (schema, defrule→clause,
+  `(decide id)` query, api). Tests: spam keyword → hide, repeated reports →
+  escalate, no rule → keep.
+- **Phase 2** — evidence accumulation + audit trail (proof tree from derivation,
+  append-only decision log, retrieval).
+- **Phase 3** — escalation + lifecycle state machine
+  (`:open → :triaged → :decided → :appealed → :final`), auto/human tiers, appeal.
+- **Phase 4** — federation (cross-instance reports, decision sharing, trust model,
+  revocation; mock fed-sx in tests).
+
+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/mod/**` and `plans/mod-on-sx.md`. Do **not** edit `spec/`,
+  `hosts/`, `shared/`, other `lib/<lang>/` dirs, `lib/stdlib.sx`, or `lib/` root.
+  May **import** from `lib/prolog/` only (its public API). Do **not** modify Prolog.
+- **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 (see how `lib/prolog/conformance.sh` drives it), pointing
+  `SX_SERVER` at `/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe`
+  (fresh worktrees have no `_build/`).
+- **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
+  (`mod: spam-keyword policy rule → :hide + 6 tests`). Push to `origin/loops/mod`.
+- **Plan file:** update Progress log (newest first) + tick boxes every commit.
+
+## mod-specific gotchas
+
+- **Decisions are proofs, not booleans.** A decision should carry *why* — the
+  matching rule / derivation — so Phase 2's audit trail can persist it. Design the
+  Phase-1 `decide` return shape with that in mind (don't return a bare keyword you
+  later have to retrofit).
+- **Policy chains backtrack.** Order matters: first matching rule wins. Make rule
+  precedence explicit and deterministic (tests will depend on it). A "no rule
+  matched" outcome must be a real, testable result (`:keep`), not a query failure
+  you forget to handle.
+- **Negative decisions need closed-world care.** "No evidence of violation" vs
+  "evidence absent" differ. Be explicit about negation-as-failure where you use it.
+- **Lifecycle state is separate from policy.** Keep the state machine (Phase 3) as
+  an SX module over the engine, not tangled into Prolog rules.
+- **Federation trust is advisory by default.** A peer's decision only binds locally
+  when `(trust peer :mod)` holds; otherwise it's a suggestion. Don't auto-apply.
+
+## 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 (`mod/...`) — short/host-colliding names
+  (`bind`, `conj`, `name`) get silently shadowed or hang the runtime.
+
+## Style
+
+- No comments in `.sx` unless non-obvious.
+- No new planning docs — update `plans/mod-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.