feat(engine): Engine::reconcile_commit and probe_manual_drift (#70)

* feat(state): extend ReconciliationEntry with adopted/skipped vectors

Adds two `Vec<String>` fields to `pearlite_state::ReconciliationEntry`,
both `#[serde(default)]` so pre-ADR `[[reconciliations]]` rows
deserialize cleanly with empty vectors. Tightens `package_count`'s
docstring to name it as the audit denominator (ADR-0014 §9).

Backfills three round-trip tests in `reconciliation::tests`:
- legacy entry without decision vectors deserializes with empty `[]`,
- populated decision vectors round-trip through TOML,
- AdoptAll with empty `skipped` round-trips.

Schema change is additive; the `ReconciliationAction` unit-variant
enum (AdoptAll / Interactive / Skipped) keeps its existing TOML
representation per ADR-0014 §7.

Refs: ADR-0014, PRD §7.3

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

* feat(engine): Engine::reconcile_commit and probe_manual_drift

Adds the write-side of reconcile (ADR-0014, M4 W1):

- `Engine::reconcile_commit(state_path, &decisions, threshold)` —
  probes via the existing adapter, classifies Manual drift through
  `pearlite_diff::{classify_pacman, classify_cargo}` against an empty
  declared `PackageSet` (the fresh-import path from PRD §11), enforces
  the `Some(N)` threshold defensively, unions adopted names into
  `state.adopted.{pacman,cargo}`, and appends one `[[reconciliations]]`
  row with a fresh `Uuid::now_v7()`. Atomic write via `StateStore`;
  `state.last_modified` set, `state.last_apply` deliberately untouched.
- `Engine::probe_manual_drift(state_path)` — read-only helper that
  returns the merged sorted-deduplicated Manual list. The CLI uses it
  to drive the threshold pre-check and per-package prompt loop without
  reaching into the engine's private probe accessor.
- `ReconcileDecisions` enum (`AdoptAll` / `Selective { adopt }`) and
  `ReconcileCommitOutcome` mirror the ADR §7 split: enum carries the
  *policy*, vectors carry the *decisions*.
- `ReconcileCommitError::{Probe, State, ThresholdExceeded}` for the
  three failure modes; threshold variant carries `count` and
  `threshold` so the CLI can surface ADR-0014 §2 wording verbatim.

Module doc now describes both reconcile entry points (read-only
import + commit). Ten new tests in `reconcile::tests`: AdoptAll happy
path, Selective partition, threshold exceeded refuses without
writing, threshold boundary allowed, `state.managed` packages stay
classified as Forgotten (not adopted), existing `state.adopted`
preserved on union, no-Manual-drift still records empty entry,
probe / state-read failure propagation, fresh `plan_id` per call.

Refs: ADR-0014, PRD §11

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

---------

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

Author: UnbreakableMJ

crates/pearlite-engine/src/errors.rs

@@ -172,6 +172,35 @@ pub enum ReconcileError {
     },
 }
 
+/// Errors emitted by
+/// [`Engine::reconcile_commit`](crate::Engine::reconcile_commit) (ADR-0014,
+/// M4 W1).
+///
+/// `reconcile_commit` resolves the Manual drift surfaced by reconcile by
+/// promoting items into `state.adopted` and recording a
+/// `[[reconciliations]]` entry. Variants identify whether the failure was
+/// on the probe side, the state read/write side, or the threshold-guard.
+#[derive(Debug, Error)]
+pub enum ReconcileCommitError {
+    /// Probing the live system failed.
+    #[error(transparent)]
+    Probe(#[from] ProbeError),
+    /// `state.toml` read or write failed.
+    #[error(transparent)]
+    State(#[from] pearlite_state::StateError),
+    /// Engine-side threshold guard: the count of Manual drift items
+    /// exceeds the supplied limit. Defense-in-depth — the CLI normally
+    /// aborts with `RECONCILE_THRESHOLD_EXCEEDED` before the engine
+    /// runs (ADR-0014 §2).
+    #[error("reconcile-commit refused: {count} Manual items exceeds threshold {threshold}")]
+    ThresholdExceeded {
+        /// Number of Manual drift items found.
+        count: u32,
+        /// Threshold the caller asked the engine to enforce.
+        threshold: u32,
+    },
+}
+
 /// Errors emitted by [`Engine::plan`](crate::Engine::plan) and friends.
 #[derive(Debug, Error)]
 pub enum EngineError {

crates/pearlite-engine/src/lib.rs

@@ -18,11 +18,12 @@ mod rollback;
 pub use apply::{ApplyContext, ApplyOutcome, FailureRecord};
 pub use bootstrap::BootstrapOutcome;
 pub use errors::{
-    ApplyError, BootstrapError, EngineError, ProbeError, ReconcileError, RollbackError,
+    ApplyError, BootstrapError, EngineError, ProbeError, ReconcileCommitError, ReconcileError,
+    RollbackError,
 };
 pub use plan::Engine;
 pub use probe::{LiveProbe, SystemProbe};
-pub use reconcile::ReconcileOutcome;
+pub use reconcile::{ReconcileCommitOutcome, ReconcileDecisions, ReconcileOutcome};
 pub use rollback::RollbackOutcome;
 
 #[cfg(any(test, feature = "test-mocks"))]