Make local plugins manageable and debuggable (#3446)

* feat(plugins): expose Paseo API to local plugins

Plugin surfaces borrow the selected host connection while subprocess handlers receive an exclusively owned IPC session, so plugins can use normal workspace and agent operations without inventing another transport.

* feat(plugins): reload global enablement safely

Treat the global plugin switch as a live daemon setting and teach plugin automation to inspect it before acting. Enabling remains permission-gated because plugin backend code can access the daemon machine and client contributions execute inside the app.

* feat(plugins): expose plugin logs

Capture plugin stdout and stderr separately from IPC so authors can debug initialization, RPC, cleanup, and crash behavior from the app or CLI. Keep a bounded tail across lifecycle recovery while preserving structured output in the daemon log.

* fix(build): order plugin dependency builds

* test(plugins): align startup and CLI expectations

docs/terminal-performance.md

@@ -24,6 +24,7 @@ Terminal frames share the daemon main event loop with all agent traffic. The `ev
 - **Coalesced output carries the LAST chunk's revision.** Snapshot replay dedup (`replayTerminalOutputAfterSnapshot`) skips buffered output with `revision <= replayRevision`; a merged batch with a lower revision would be wrongly skipped (lost output).
 - **The input-mode tracker runs once per process boundary, not per hop.** The worker owns the authoritative tracker; the daemon caches the replay preamble from `getTerminalState` responses and `snapshotReady` messages. Do not reintroduce a per-chunk `feed()` on the daemon main loop.
 - **Snapshot catch-up is backpressure-gated.** A stream falls back to a full snapshot only when `outputBytesSinceSnapshot > MAX_TERMINAL_OUTPUT_FRAME_BYTES` (256KB) **and** the client transport reports `bufferedAmount > MAX_CLIENT_BUFFERED_BYTES` (4MB). A client that keeps draining streams continuously, no matter how much output is produced. Before this gate existed, every 256KB of build output dropped a frame and forced a full JSON cell-grid snapshot (~200k objects across IPC) — the historical source of spiky lag and GC hitches.
+- **Plugin daemon sessions report IPC queue bytes.** Their virtual socket increments `bufferedAmount` before `process.send` and decrements it only in the send callback. Text and binary frames share that ordered queue, so the normal snapshot catch-up and physical high-water gates remain valid for server-side plugin SDK traffic.
 - **Client output writes are not serialized per frame.** The emulator runtime drains contiguous plain writes straight into xterm (which buffers internally). Only barrier ops (`clear`, `snapshot`, `suppressInput` writes) wait — behind a zero-length sentinel write — so resets can't interleave with in-flight output.
 - **Terminal size has one daemon-owned claimant.** Focus and direct interaction send a `claim`; later geometry changes from that connection send `update`. A claim transfers ownership even when the dimensions are unchanged, while an update from any other connection is ignored. This lets an owning pane follow splits and keyboard insets without allowing an idle phone or browser to steal the PTY size.