feat: add session correlation fields to BoundaryLog proto (#24809)

1 of 9 [next >>](https://github.com/coder/coder/pull/24811)

RFC: [Bridge ↔ Boundaries Correlation
RFC](https://www.notion.so/Bridge-Boundaries-Correlation-313d579be59281f3b4efdbfd6896775a)

Adds three new proto fields for boundary session correlation.

**`ReportBoundaryLogsRequest`**
- `session_id` (string, field 2) — UUID generated by boundary at
startup,
  shared across all batches from a single run.
- `confined_process` (string, field 3) — name of the confined process
  (e.g. `claude-code`, `codex`, `copilot`).

**`BoundaryLog`**
- `sequence_number` (uint64, field 4) — monotonically increasing counter
  per session, primary ordering key when boundary is in use.

`BoundaryLog.time` already existed at field 2; no change needed there.

API version bumped to v2.9.

No behaviour change in coderd or the agent. This is a pure schema bump
that the boundary repo will consume in its own stack.

> Generated by Coder Agents

tailnet/proto/version.go

@@ -64,9 +64,14 @@ import (
 // API v2.8:
 //   - Added support for pre-created sub agents on the Agent API.
 //   - Added support for UpdateAppStatus on the Agent API.
+//
+// API v2.9:
+//   - Added session_id and confined_process fields to
+//     ReportBoundaryLogsRequest on the Agent API.
+//   - Added sequence_number field to BoundaryLog on the Agent API.
 const (
 	CurrentMajor = 2
-	CurrentMinor = 8
+	CurrentMinor = 9
 )
 
 var CurrentVersion = apiversion.New(CurrentMajor, CurrentMinor)