feat(a2a): steer session citations toward inspect_peer (#1373)

* feat(a2a): steer session citations toward inspect_peer

Copy-reference prose and markdown /sessions/<id> links both parse to hub
ids; MCP/CLI descriptions and flavor prompts forbid treating them as local
FS paths so agents call inspect_peer first (tiann/hapi#1370).

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(a2a): fail closed on ambiguous session citations

Codex #1373: do not silently pick ids[0] when a paste contains multiple
/sessions/ links (shared by inspect_peer and ping_peer). Also strip
trailing prose punctuation from bare citation ids.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(a2a): prefer Copy-reference path over title /sessions/

Codex #1373 MINOR: titles containing /sessions/<other> must not make
normalizeSessionIdPrefix fail closed on an otherwise valid paste.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(a2a): do not short-circuit multi-citation Copy-reference pastes

Codex #1373 MAJOR: only treat parenthesized Copy-reference as canonical
when the paste is that citation alone (plus optional steer suffix).

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

cli/src/codex/utils/systemPrompt.ts

@@ -6,6 +6,7 @@
  */
 
 import { trimIdent } from '@/utils/trimIdent';
+import { buildSessionCitationSteerInstruction } from '@hapi/protocol/sessionCitation';
 
 /**
  * Title instruction for Codex to call the hapi MCP tool.
@@ -19,7 +20,10 @@ export const TITLE_INSTRUCTION = trimIdent(`
     Do not rename the chat for routine progress, substeps, implementation details, or a slightly better wording.
     Rename only when the user's primary objective changes substantially and the existing title would be misleading.
     When you create or find a local image file that the user should see, call functions.hapi__display_image with the image path. If that exact tool name is unavailable, use an equivalent alias such as hapi__display_image, mcp__hapi__display_image, or hapi_display_image.
-    When the user cites another HAPI session as [title](/sessions/<id>) (or a bare /sessions/<id>), extract that <id>. Call functions.hapi__inspect_peer with sessionIdPrefix=<id> to read metadata and recent messages; call functions.hapi__ping_peer with sessionIdPrefix=<id> and a message to nudge or hand off. Prefer these over JWT+curl. Shell fallbacks: hapi inspect-peer <id> / hapi ping-peer <id> <message>.
+    ${buildSessionCitationSteerInstruction({
+        inspectTool: 'functions.hapi__inspect_peer',
+        pingTool: 'functions.hapi__ping_peer',
+    })}
 `);
 
 /**