feat(ce-ideate): subject gate, surprise-me, and warrant contract (#671)

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

AGENTS.md

@@ -27,15 +27,15 @@ bun run release:validate  # check plugin/marketplace consistency
 - **Output Paths:** Keep OpenCode output at `opencode.json` and `.opencode/{agents,skills,plugins}`. For OpenCode, command go to `~/.config/opencode/commands/<name>.md`; `opencode.json` is deep-merged (never overwritten wholesale).
 - **Scratch Space:** Default to OS temp. Use `.context/` only when explicitly justified by the rules below.
   - **Default: OS temp** — covers most scratch, including per-run throwaway AND cross-invocation reusable, regardless of whether a repo is present or whether other skills may read the files. A stable OS-temp prefix handles cross-skill and cross-invocation coordination equally well as an in-repo path; repo-adjacency is rarely the relevant property.
-    - **Per-run throwaway**: `mktemp -d -t <prefix>-XXXXXX` (OS handles cleanup). Use for files consumed once and discarded — captured screenshots, stitched GIFs, intermediate build outputs, recordings, delegation prompts/results, single-run checkpoints.
-    - **Cross-invocation reusable**: stable path like `"${TMPDIR:-/tmp}/compound-engineering/<skill-name>/<run-id>/"` — **not** `mktemp -d` — so later invocations of the same skill can discover sibling run-ids. Use for caches keyed by session, checkpoints meant to survive context compaction within a loose session, or any state where later runs of the same skill need to locate prior outputs.
+    - **Per-run throwaway**: `mktemp -d -t <prefix>-XXXXXX` (OS handles cleanup). Use for files consumed once and discarded — captured screenshots, stitched GIFs, intermediate build outputs, recordings, delegation prompts/results, single-run checkpoints. The resulting path is opaque (on macOS it resolves under `$TMPDIR`/`/var/folders/...`) — that is appropriate for throwaway files users are not meant to access.
+    - **Cross-invocation reusable**: stable path `/tmp/compound-engineering/<skill-name>/<run-id>/` — **not** `mktemp -d` — so later invocations of the same skill can discover sibling run-ids. Use `/tmp` directly rather than `$TMPDIR` so paths stay accessible: `$TMPDIR` on macOS resolves to `/var/folders/64/.../T/`, which is hostile for users who want to inspect checkpoints, grep them, or copy them out. The per-user isolation `$TMPDIR` provides is not valuable for cross-invocation reusable scratch where users are the intended audience. Use for caches keyed by session, checkpoints meant to survive context compaction within a loose session, or any state where later runs of the same skill need to locate prior outputs.
   - **Exception: `.context/`** — use only when the artifact is genuinely bound to the CWD repo AND meets at least one of:
     - (a) **User-curated**: the user is expected to inspect, manipulate, or manually curate the artifact outside the skill (e.g., a per-repo TODO database, a per-spec optimization log that survives across sessions on the same checkout).
     - (b) **Repo+branch-inseparable**: the artifact's meaning is inseparable from this specific repo or branch (e.g., branch-specific resume state that a user expects to pick up again in the same checkout).
     - (c) **Path is core UX**: surfacing the artifact path back to the user is a core part of the skill's output and that path is easier to communicate as a repo-relative location than an OS-temp one.
     Namespace under `.context/compound-engineering/<workflow-or-skill-name>/`, add a per-run subdirectory when concurrent runs are plausible, and decide cleanup behavior per the artifact's lifecycle (per-run scratch clears on success; user-curated state persists). "Shared between skills" is not by itself sufficient — OS temp handles that equally well.
   - **Durable outputs** (plans, specs, learnings, docs, final deliverables) belong in `docs/` or another repo-tracked location, not in either scratch tier.
-  - **Cross-platform note:** `"${TMPDIR:-/tmp}"` is the portable prefix — `$TMPDIR` resolves on macOS (per-user path in `/var/folders/`) and may be set on Linux; the `/tmp` fallback covers unset cases. `mktemp -d -t <prefix>-XXXXXX` works on macOS, Linux, and WSL. Skills authored here assume Unix-like shells; native Windows is not a current target.
+  - **Cross-platform note:** `/tmp` is writable on macOS (symlink to `/private/tmp`), Linux, and WSL. `mktemp -d -t <prefix>-XXXXXX` also works on all three. Skills authored here assume Unix-like shells; native Windows is not a current target.
 - **Character encoding:**
   - **Identifiers** (file names, agent names, command names): ASCII only -- converters and regex patterns depend on it.
   - **Markdown tables:** Use pipe-delimited (`| col | col |`), never box-drawing characters.