fix(agent): send_chat matcher requires single-word recipient

Bug: 'tell me a haiku about flowcharts' matched send_chat with
target='me a haiku' / body='flowcharts', producing the bogus
"I don't know who 'me a haiku' is" reply and silently swallowing
all non-tool prompts that started with tell/ask. The LLM fallback
never ran, so [llm] telemetry from wave 3 never fired in tests.

Fix: tighten the matcher to require a single-word [A-Za-z]+ name
between the verb and that/about/:. Drop the substring search in the
directory; require an exact match. Now 'tell me a haiku about X'
falls through to llmFallback as intended.

qa/_wave3_verify.mjs

@@ -55,11 +55,13 @@ else fail("wave3_studio_draft_lands_via_split_post", `posts=${JSON.stringify(flo
 
 console.log("\n=== watch-out 2: LLM telemetry shows in console ===");
 await p.locator(".tab").filter({ hasText: /Assistant/i }).first().click();
-await p.waitForTimeout(3000);
+await p.waitForSelector(".agent-composer textarea", { timeout: 15000 });
+await p.waitForTimeout(2000);
 const txt = p.locator(".agent-composer textarea").first();
-await txt.fill("Briefly: what is EA2?");
+// Genuinely non-tool prompt so routeAgentInput falls through to llmFallback.
+await txt.fill("tell me a haiku about flowcharts");
 await txt.press("Enter");
-await p.waitForTimeout(10000);
+await p.waitForTimeout(14000);
 const llmConsoleEntries = consoleMsgs.filter(m =>
   m.type === "warning" || m.type === "info"
 ).filter(m => m.text.includes("[llm]"));