Show similar earlier incidents and let notes be marked as the fix

The incident view gets a "Seen before" section from the server's new
/similar endpoint; an older server without it just shows nothing. C adds a
note as the resolution note, alongside c for a plain note. Needs the
server release that adds /similar.

Claude-Session: https://claude.ai/code/session_01MMados3BD1oSjevHxbmVqU

internal/api/client.go

@@ -276,6 +276,18 @@ func (c *Client) GetIncidentTimeline(id int64) ([]IncidentEvent, error) {
 	return events, c.do(req, &events)
 }
 
+// GetSimilarIncidents lists earlier resolved incidents that look like this one
+// and have notes. Servers before the similar-incidents endpoint answer 404; the
+// caller treats any error as "nothing to show".
+func (c *Client) GetSimilarIncidents(id int64) ([]SimilarIncident, error) {
+	req, err := c.newRequest(http.MethodGet, fmt.Sprintf("/api/incidents/%d/similar", id))
+	if err != nil {
+		return nil, err
+	}
+	var similar []SimilarIncident
+	return similar, c.do(req, &similar)
+}
+
 func (c *Client) AcknowledgeIncident(id int64) (*Incident, error) {
 	req, err := c.newRequest(http.MethodPost, fmt.Sprintf("/api/incidents/%d/acknowledge", id))
 	if err != nil {
@@ -357,10 +369,11 @@ func (c *Client) UnarchiveIncident(id int64) error {
 	return c.do(req, nil)
 }
 
-// AddNote appends a note to the incident's timeline.
-func (c *Client) AddNote(incidentID int64, content string) (*IncidentEvent, error) {
+// AddNote appends a note to the incident's timeline. pinned files it as the
+// resolution note: what fixed the incident, shown on similar ones later.
+func (c *Client) AddNote(incidentID int64, content string, pinned bool) (*IncidentEvent, error) {
 	req, err := c.newRequestWithBody(http.MethodPost,
-		fmt.Sprintf("/api/incidents/%d/notes", incidentID), map[string]string{"content": content})
+		fmt.Sprintf("/api/incidents/%d/notes", incidentID), map[string]any{"content": content, "pinned": pinned})
 	if err != nil {
 		return nil, err
 	}