feat: use tool calls for answer extraction

docs/architecture.md

@@ -16,7 +16,7 @@ The codebase is split so the implementation reads through file boundaries and na
 - `src/index.ts` — extension entrypoint
 - `src/ask-tool.ts` — tool registration, non-interactive fallback, transcript rendering, ask payload capture
 - `src/answer-commands.ts` — `/answer`, `/answer:again`, and `/ask:replay` command wiring
-- `src/answer-extraction.ts` — configured extraction model selection and raw-JSON extraction retries
+- `src/answer-extraction.ts` — configured extraction model selection, synthetic `ask_user` tool-call extraction, and tolerant text fallback
 - `src/ask-payload-store.ts` — branch-aware persisted ask payload lookup
 - `src/notifications.ts` — best-effort ask notification payload rendering and channel execution
 - `src/remote-ask.ts` — package-prefixed local event contract, active-flow registry, and explicit remote submission validation

docs/configuration.md

@@ -112,7 +112,7 @@ These settings affect only the `/answer` command. Normal `ask_user` tool calls d
 
 - type: integer from `0` to `3`
 - default: `1`
-- effect: number of retry attempts after raw JSON parsing fails; retries include the parse error and previous response as feedback
+- effect: number of retry attempts after the model omits `ask_user`, returns invalid tool arguments, or produces an invalid JSON text fallback; retries include the previous error and response as feedback
 
 ## Behaviour
 

docs/contract.md

@@ -207,7 +207,7 @@ This document defines the stable external behavior. It does not explain internal
 - on the review tab, `Submit` and `Cancel` preview notes only for answered questions
 - on the review tab, `Elaborate` preview expands to all question notes and all option notes, including notes on unselected options
 - transcript-friendly call and result rendering
-- `/answer` command to extract a raw-JSON `AskParams` form from the latest completed assistant message and open the ask UI
+- `/answer` command to convert the latest completed assistant message into an `AskParams` form through a synthetic `ask_user` tool call and open the ask UI
 - `/answer` extraction may use an internal `freeform: true` option for open-ended questions with no explicit choices; these render as user-input-only questions with the label `Type your answer:`, no numbered option row, and no selection caret; this marker is not part of the public `ask_user` tool contract
 - `/answer:again` command to replay the latest `/answer`-extracted form on the current branch
 - `/ask:replay` command to replay the latest real `ask_user` form on the current branch
@@ -286,7 +286,8 @@ See [`remote-events.md`](remote-events.md) for payload shapes, examples, and a l
 
 - valid `ask_user` payloads are persisted as branch custom entries before the UI opens, so `/ask:replay` can reopen them after cancel, `/resume`, or `/tree`
 - `/answer` scans the current branch for the latest assistant message; if that message did not finish with `stop`, extraction is refused
-- `/answer` expects the extractor to return raw JSON only; JSON parse failures are retried according to `answer.extractionRetries`, then reported to the user without opening the ask UI
+- `/answer` sends the preceding user message as context with the latest assistant text and asks the extractor for one synthetic `ask_user` tool call
+- missing or invalid tool calls are retried according to `answer.extractionRetries`; raw or fenced JSON text remains supported as a last-resort fallback
 - `{ "questions": [] }` from extraction means no questions were found and is not treated as an invalid ask payload
 - command-flow cancellation closes with a notification and does not send a message to the agent
 - submitted or elaborated command-flow results are sent back with user-message semantics