docs(wiki): add pi end-to-end proof to agent-harness

agent-harness.md listed only zot's end-to-end proof (zot_rpc_smoke.rs,
ignored, ZOT_BIN-gated). pi now has better default CI coverage via
pi_spawn_live.rs (unignored, runs every test run), plus the new
default_agent_args unit tests proving the autospawn argv contract.

Also moves the autospawn argv reference into its own bullet for clarity.

docs/wiki/agent-harness.md

@@ -39,8 +39,13 @@ Where it lives:
   `crates/colibri-daemon/src/socket.rs` (`default_agent_args`,
   `autospawn_agent_if_configured`)
 - wire format (verified against real zot): [agent-events-reference](./agent-events-reference.md)
-- end-to-end proof: `crates/colibri-daemon/tests/zot_rpc_smoke.rs`
-  (`#[ignore]`, `ZOT_BIN`-gated)
+- end-to-end proof, zot: `crates/colibri-daemon/tests/zot_rpc_smoke.rs`
+  (`#[ignore]`, `ZOT_BIN`-gated — needs the real zot binary)
+- end-to-end proof, pi: `crates/colibri-daemon/tests/pi_spawn_live.rs`
+  (unignored, runs in every `cargo test` — uses `sample-pi-agent.py` which
+  emits colibri-pi-events taxonomy verified against real pi)
+- autospawn argv contract: `crates/colibri-daemon/src/socket.rs`
+  (`default_agent_args` unit tests — zot→rpc, pi→--mode json)
 
 OOTB default harness is **zot**; pi remains a supported fallback
 (`COLIBRI_AUTOSPAWN_BINARY=pi`).