feat(capture): remove summary->ai-sessions write path

ai-sessions#13: capture's `summary` field wrote a frontmatter shape
(title/harness/fidelity/captured_at/repos_touched) that ai-sessions'
own extract/audit pipeline can't parse -- silently invisible to that
repo's own audit tooling, and bypassing its redaction + Stage2
completeness gates by construction. Only 5 files ever landed this way
over 3 weeks; the summary capability's whole value (speed) fights
ai-sessions' whole value (redacted, audited, complete), so kill it
rather than build a second parse branch.

capture now persists insights -> brain and action items -> Gitea
tickets only. Removes Summary/SummaryResult/SummaryWriter and all
wiring (service, REST body, MCP tool schema); close-session updated to
stop assembling a summary payload. specs/capture-*.md kept as historical
record with a superseded note -- the feature shipped and is documented,
just no longer current behaviour.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WPdSHbp9Utb2hPFm9wDG59

ingestion/internal/capturehttp/handler.go

@@ -55,7 +55,6 @@ type request struct {
 	Context  contextBody   `json:"context"`
 	Insights []insightBody `json:"insights"`
 	Tickets  []ticketBody  `json:"tickets"`
-	Summary  *summaryBody  `json:"summary,omitempty"`
 	DryRun   bool          `json:"dry_run"`
 }
 
@@ -82,12 +81,6 @@ type ticketBody struct {
 	Body   string `json:"body,omitempty"`
 }
 
-type summaryBody struct {
-	Title        string   `json:"title"`
-	Body         string   `json:"body"`
-	ReposTouched []string `json:"repos_touched,omitempty"`
-}
-
 // ServeHTTP authenticates, derives origin, runs the use-case, and maps the
 // result to an HTTP status.
 func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
@@ -183,11 +176,6 @@ func (b request) toInput() capture.CaptureInput {
 			Repo: t.Repo, Action: t.Action, Number: t.Number, Title: t.Title, Body: t.Body,
 		})
 	}
-	if b.Summary != nil {
-		in.Summary = &capture.Summary{
-			Title: b.Summary.Title, Body: b.Summary.Body, ReposTouched: b.Summary.ReposTouched,
-		}
-	}
 	return in
 }
 
@@ -204,9 +192,6 @@ func statusFor(rec capture.CaptureReceipt) int {
 	for _, t := range rec.Tickets {
 		count(&ok, &fail, t.OK)
 	}
-	if rec.Summary != nil {
-		count(&ok, &fail, rec.Summary.OK)
-	}
 	switch {
 	case fail == 0:
 		return http.StatusOK