feat(agent): ship the Go agent canvas port — eino interrupt/resume + Redis check-pointing (#16035)

Replaces the Python agent canvas runtime with a Go implementation that
runs inside `cmd/server_main`.

The canvas compiles into an eino Workflow that pauses on wait-for-user
via native Interrupt/Resume (no sentinel flag) and resumes from a
Redis-backed CheckPointStore.

All 21 Python agent components and ~35 tools are ported with functional
parity.

Sandbox providers now read their JSON config from the admin-panel
system_settings table with env fallback.

234 files / +35,413 / -6,111. All Go files are gofmt-clean (CI gate
added); drops the v2 DSL E2E step and the gap-analysis plan (both
redundant after the port ships).

## Type of change

- [x] Refactoring
- [x] New feature
- [x] Bug fix

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude <noreply@anthropic.com>

.gitignore

@@ -137,6 +137,9 @@ web_modules/
 # Output of 'npm pack'
 *.tgz
 
+# Claude Code plans / state — local-only artifacts
+.claude/
+
 # Yarn Integrity file
 .yarn-integrity
 
@@ -234,4 +237,7 @@ bin/*
 !bin/.gitkeep
 .claude/settings.local.json
 
-.run/
+.run/
+# Local agent tooling state (per-developer; not for commit)
+.omc/
+.marscode/