Stream workspace action progress over WebSockets (#366)

Workspace action progress was previously refreshed only by the
five-second polling loop, which made stop, update-and-start, and
update-and-restart operations appear stale between polls.

We added a workspace progress watcher that uses Coder's workspace and
build-log WebSockets on supported deployments. The remote environment
uses those events only for the progress description, while the workspace
poller remains responsible for workspace and agent state.

We added version gating and failure handling so older deployments and
unavailable WebSocket connections continue through the existing polling
path. We also added coverage for streaming output, state isolation,
lifecycle cleanup, and fallback behavior.

- resolves https://linear.app/codercom/issue/JET-1/

Author: fioan89

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ## Unreleased
 
+### Changed
+
+- stream build status and provisioner output while updating, restarting, or stopping workspaces, falling back to
+  polling for older Coder deployments
+
 ## 0.9.5 - 2026-10-30
 
 ### Added