[task]
role = "edit-local"
agent-id = "kei-prune-scaffold-w14"

[scope]
files-whitelist = ["_primitives/_rust/kei-prune/**"]
files-denylist = ["_primitives/_rust/Cargo.toml"]

[verification]
cargo-check-crates = ["kei-prune"]
cargo-test-crates = ["kei-prune"]
test-count-min = 8

[output]
report-fields-required = [
    "files-touched",
    "cargo-check",
    "cargo-test",
]

[body]
text = """
Create new primitive `kei-prune` — retire unused agents / primitives based on
kei-ledger usage stats. Mirrors biological pruning: mozg забывает то что не
активировалось достаточно долго.

## Design

1. Engine-native via kei-entity-store. No new schema (just queries over
   existing ledger `agents` table).

2. Public API:
   ```rust
   pub struct PruneCandidate { id: i64, dna: String, last_used_ts: i64, age_days: i64 }
   pub fn candidates(conn: &Connection, now: i64, min_idle_days: u32) -> Result<Vec<PruneCandidate>, Error>;
   pub fn mark_retired(conn: &Connection, id: i64, now: i64) -> Result<(), Error>;
   ```

3. CLI:
   - `kei-prune list --idle-days 90` — JSON array of candidates
   - `kei-prune mark --id 5` — mark retired (sets status='retired', no delete)
   - `kei-prune stats` — summary: active / idle / retired counts

4. Pure metadata primitive — DOES NOT delete anything. Marks ledger row
   status='retired'. Downstream tooling (archive/compact) can act on marker.

## Tests (≥8)

- candidates_returns_empty_on_fresh_db
- candidates_excludes_active_rows
- candidates_returns_idle_over_threshold
- candidates_respects_min_idle_days
- mark_retired_updates_status
- mark_retired_idempotent
- stats_counts_buckets
- retired_rows_excluded_from_candidates

## Constructor Pattern
Every file ≤200 LOC, every fn ≤30 LOC. Deps: kei-entity-store path,
rusqlite workspace, clap workspace, serde workspace, thiserror workspace.

## IMPORTANT — standalone [workspace] escape hatch
Add empty [workspace] table to crate's Cargo.toml (inside your whitelist)
so cargo check/test work before orchestrator registers in workspace.
Orchestrator will remove on merge.
"""