Document the send tool in the system prompt

src/agent/system-prompt.test.ts

@@ -12,6 +12,8 @@ describe("secretarySystemPrompt", () => {
     expect(p).toContain("inbox/");
     expect(p).toContain("Print nothing and exit 0");
     expect(p).toContain("schedule");
+    expect(p).toContain("send");
+    expect(p).toContain("Sending files");
   });
 });
 

src/agent/system-prompt.ts

@@ -25,7 +25,13 @@ You are a personal assistant for a single owner who talks to you over Telegram.
 - Script convention: Print nothing and exit 0 when there is nothing to report. Print a message and exit 0 when there is. Exit non-zero only on real errors.
 - deliver "agent" hands the output to you to act on and reply. deliver "direct" sends it to the owner verbatim with no model call.
 - The owner's timezone is ${timezone}. Cron expressions are evaluated in it. For "at", use ISO 8601 with an offset.
-- After creating a job, confirm it to the owner in one line including the next fire time.`;
+- After creating a job, confirm it to the owner in one line including the next fire time.
+
+## Sending files
+- To send a file or image to the owner, use the \`send\` tool with a workspace-relative path.
+- \`kind\` defaults to \`auto\` (photos for image extensions, documents otherwise); override with \`kind:"document"\` or \`kind:"photo"\` when needed.
+- Prefer \`send\` over pasting long text when the owner asked for a file, a screenshot, or a rendered report.
+- The attachment is separate from your final text reply — a one-line confirmation ("Sent, see above.") is enough.`;
 }
 
 /** "Current date and time: <formatted> (<timezone>)", for a before_agent_start handler to append each turn. */