worker: implement session explore extract worker

.yoi/tickets/00001KXMK7YMC/item.md

@@ -1,9 +1,11 @@
 ---
 title: 'session-explore feature付きextract workerを実装する'
-state: 'planning'
+state: 'closed'
 created_at: '2026-07-16T04:34:01Z'
-updated_at: '2026-07-17T18:10:00Z'
+updated_at: '2026-07-18T01:35:46Z'
 assignee: null
+queued_by: 'yoi ticket'
+queued_at: '2026-07-18T01:12:22Z'
 ---
 
 ## 背景

.yoi/tickets/00001KXMK7YMC/resolution.md

@@ -0,0 +1,10 @@
+Implemented the session-explore-backed extract worker.
+
+The extract worker now receives an immutable `SessionReferenceView` snapshot and only the `builtin:session-explore` tool surface. It can search/read bounded evidence, stage one flat candidate per `stage_candidate` call with resolved source anchors, and finish cleanly with `finish_extraction` including the no-candidate path.
+
+Validation passed:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`

.yoi/tickets/00001KXMK7YMC/thread.md

@@ -57,4 +57,101 @@ Rescoped from broad Overview-first extract implementation to the worker implemen
 Design updated: abandon the old batch `write_extracted` / `decisions` / `discussions` / `attempts` / `requests` staging direction. Extract now stages flat candidate records with `stage_candidate` and finishes with `finish_extraction`. The older dependency on 00001KXNYXNM6 is historical; the active schema dependency is 00001KXRM6G0G.
 
 
+---
+
+<!-- event: intake_summary author: hare at: 2026-07-18T01:12:22Z -->
+
+## Intake summary
+
+Marked ready by `yoi ticket state`.
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: planning to: ready reason: cli_state field: state -->
+
+## State changed
+
+Marked ready by `yoi ticket state`.
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: ready to: queued reason: queued field: state -->
+
+## State changed
+
+Ticket を `yoi ticket` が queued にしました。
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:12:22Z from: queued to: inprogress reason: cli_state field: state -->
+
+## State changed
+
+State changed to `inprogress`.
+
+
+---
+
+<!-- event: implementation_report author: hare at: 2026-07-18T01:35:46Z -->
+
+## Implementation report
+
+Implemented the session-explore-backed memory extract worker.
+
+Changes:
+- Added `builtin:session-explore` with `search_evidence`, `read_evidence`, `stage_candidate`, and `finish_extraction`.
+- Extract worker now builds an immutable `SessionReferenceView` at extract start and enables only session-explore tools for the internal worker.
+- Added overview-first / evidence-index-second extract input rendering over the reference view.
+- `stage_candidate` writes one flat staging record per call, resolving evidence ids into bounded staging evidence and `SourceEvidenceRef` anchors.
+- `finish_extraction` supports normal no-candidate completion with `staged_count = 0`.
+- Updated `memory_extract_system.md` to the session-explore / stage / finish contract.
+- Added a single-candidate staging helper in `memory::extract::staging`.
+- Updated extract-trigger tests to use `finish_extraction` and added session-explore unit tests.
+
+Validation:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`
+
+
+---
+
+<!-- event: state_changed author: "yoi ticket" at: 2026-07-18T01:35:46Z from: inprogress to: done reason: cli_state field: state -->
+
+## State changed
+
+State changed to `done`.
+
+
+---
+
+<!-- event: state_changed author: hare at: 2026-07-18T01:35:46Z from: done to: closed reason: closed field: state -->
+
+## State changed
+
+Ticket を closed にしました。
+
+
+---
+
+<!-- event: close author: hare at: 2026-07-18T01:35:46Z status: closed -->
+
+## 完了
+
+Implemented the session-explore-backed extract worker.
+
+The extract worker now receives an immutable `SessionReferenceView` snapshot and only the `builtin:session-explore` tool surface. It can search/read bounded evidence, stage one flat candidate per `stage_candidate` call with resolved source anchors, and finish cleanly with `finish_extraction` including the no-candidate path.
+
+Validation passed:
+- `cargo fmt --check`
+- `cargo test -p worker`
+- `cargo test -p memory`
+- `nix build .#yoi`
+- `yoi ticket doctor`
+
+
 ---