Capture tasks, with one intake seam mail can call later (#130)

A task is not a fact and not a note. A fact is a claim about the world that a
correction supersedes; a note is something to recall by meaning. A task is work
with a lifecycle, and the read that matters is "everything outstanding right
now" — which over an append-only log would mean replaying history on every
question. So: a tasks table, migration #14, statuses candidate/open/done/dropped
that each move forward exactly once.

Dedupe is on normalised text among LIVE rows only, via a partial unique index.
That is the property the mail side needs: an extractor may call CaptureTask for
every message it reads, as often as it likes, without growing the list — while a
weekly errand is still capturable again once the last one is done.

Three ways in, one seam. ipc.CaptureTaskReq is it: the voice path
(router.ParseTaskCapture on an explicit marker — "добавь в задачи …", never
"надо бы поспать"), the /tasks form, and the email reader from #246 when it
exists. Mail-derived items set Source "email:<account>", Status "candidate" and
Evidence to whatever makes the row reviewable; a candidate is inert until he
confirms it on /tasks, and Maven names it as unconfirmed when she recites the
list rather than putting words in his mouth.

No new intent — the router enum is a contract with the relabelling prompt, so
capture rides the note intent and the list rides a query source, both matched
deterministically like the calendar and plan matchers already are.

Nothing here speaks. No tick rule reads tasks; the list is answered when asked
about, which is why /tasks POST is not step-up gated the way /tools and
/routines are — a task write moves no boundary.

Vikunja #130

internal/ipc/api.go

@@ -93,6 +93,63 @@ type WriteFactReq struct {
 	Subject string `json:"subject,omitempty"`
 }
 
+// Task — one captured piece of work (Vikunja #130). Status is
+// "candidate" (Maven derived it and it is unconfirmed), "open" (his work),
+// "done" or "dropped". Source is provenance in the facts vocabulary:
+// "tap:voice", "tap:web", "email:<account>". Evidence is the trail a derived
+// task came from, empty for anything he stated himself.
+type Task struct {
+	ID        int64      `json:"id"`
+	CreatedTs time.Time  `json:"created_ts"`
+	Text      string     `json:"text"`
+	Source    string     `json:"source"`
+	Evidence  string     `json:"evidence,omitempty"`
+	Status    string     `json:"status"`
+	Due       *time.Time `json:"due,omitempty"`
+	Weight    int        `json:"weight,omitempty"`
+	Resolved  *time.Time `json:"resolved,omitempty"`
+}
+
+// CaptureTaskReq — THE INTAKE SEAM. Everything that captures a task goes
+// through this one shape: the voice path, the web form, and (Vikunja #246) the
+// email reader, which has not been built yet.
+//
+// An extractor that reads mail sets Source "email:<account>", Status
+// "candidate", and Evidence to whatever makes the task reviewable (the subject
+// line). It must NOT set Status "open" — work Maven inferred from something she
+// read is a suggestion until the owner confirms it on the /tasks page. Capture
+// is idempotent on normalised text among live tasks, so re-reading the same
+// mailbox is free.
+type CaptureTaskReq struct {
+	Text     string     `json:"text"`
+	Source   string     `json:"source"`
+	Evidence string     `json:"evidence,omitempty"`
+	Status   string     `json:"status,omitempty"` // "" ⇒ open
+	Due      *time.Time `json:"due,omitempty"`
+	Weight   int        `json:"weight,omitempty"`
+	Ts       time.Time  `json:"ts"`
+}
+
+// CaptureTaskResp — Created is false when the same live task already existed,
+// in which case ID is the existing row. A caller tells the owner "уже в
+// списке" rather than claiming it saved something new.
+type CaptureTaskResp struct {
+	ID      int64 `json:"id"`
+	Created bool  `json:"created"`
+}
+
+type listTasksReq struct {
+	Status string `json:"status"` // "" all | "live" | candidate|open|done|dropped
+}
+type listTasksResp struct {
+	Tasks []Task `json:"tasks"`
+}
+type setTaskStatusReq struct {
+	ID     int64     `json:"id"`
+	Status string    `json:"status"`
+	Ts     time.Time `json:"ts"`
+}
+
 // idReq — methods keyed by a single id.
 type idReq struct {
 	ID int64 `json:"id"`
@@ -294,6 +351,18 @@ type CoreAPI interface {
 	// loop takes the schedule from there — no reminder is created (Vikunja #366).
 	AcceptProposedRoutine(ctx context.Context, id int64) error
 
+	// CaptureTask records a task. See CaptureTaskReq — this is the single
+	// intake seam for the voice path, the web form and the future email
+	// extractor. Idempotent per live normalised text; the response says
+	// whether a row was actually created.
+	CaptureTask(ctx context.Context, req CaptureTaskReq) (CaptureTaskResp, error)
+	// ListTasks returns tasks in one status, newest first. "" is every row,
+	// "live" is candidate + open (outstanding work).
+	ListTasks(ctx context.Context, status string) ([]Task, error)
+	// SetTaskStatus moves a task forward once: candidate→open|dropped,
+	// open→done|dropped. Any other move is refused.
+	SetTaskStatus(ctx context.Context, id int64, status string, ts time.Time) error
+
 	// TickTrace returns the most recent tick's rule trace. The daemon caches
 	// this after every tick; the store adapter returns an error (trace is not
 	// persisted — it's a daemon-level cache).