feat: Ambient Code Platform session backend

[tiwillia]

Summary

• Add AmbientSessionBackend implementing the SessionBackend interface for remote agent sessions via the ACP public API
• Create ambient-workflow/ with adapted /boss.plan, /boss.check, /boss.ignite commands for ACP sessions (no tmux dependencies, uses BOSS_URL and AGENT_NAME env vars)
• Wire workflow config into the backend so all spawned ambient sessions automatically get activeWorkflow and environmentVariables set on the K8s CR
• Add Initial Prompt and Repos fields to the create agent dialog when ambient backend is selected
• Cascade-delete the backing ACP session when an agent is removed
• Preserve original agent name casing instead of lowercasing on creation
• Hide tmux-specific controls (approval prompt, keystroke injection) for ambient-backed agents

Backend changes

File	Change
session_backend.go	AmbientCreateOpts with WorkflowRef, Repos, EnvVars fields
session_backend_ambient.go	Full SessionBackend implementation against ACP public API; CreateSession includes activeWorkflow, environmentVariables, and repos in the request body
server.go	Read AMBIENT_WORKFLOW_* and COORDINATOR_EXTERNAL_URL env vars
handlers_agent.go	Add repos/task to create request; cascade-delete sessions on agent removal; preserve name casing
lifecycle.go	Use resolveAgentName instead of ToLower for agent map keys
deploy/openshift/configmap.yaml	Add workflow and coordinator URL env vars

Workflow files (ambient-workflow/)

File	Description
.ambient/ambient.json	Workflow manifest with system prompt (full protocol, API reference)
.claude/commands/boss.ignite.md	Adapted for ACP: $BOSS_URL, $AGENT_NAME env vars, no tmux
.claude/commands/boss.check.md	Adapted: $BOSS_URL env var, $AGENT_NAME fallback
.claude/commands/boss.plan.md	Copied as-is (no tmux dependencies)
CLAUDE.md	Behavioral guidelines for multi-agent coordination

Frontend changes

• Create agent dialog shows "Initial Prompt" and "Repos" fields when ambient backend is selected (replacing "Working Directory" for tmux)
• Hide tmux Controls section (approval, keystroke injection) for ambient agents

Test plan

• go test -race ./internal/coordinator/ passes
• npm run build succeeds
• Manual: spawn ambient agent via API, verify activeWorkflow, environmentVariables, and repos appear on the K8s AgenticSession CR
• Manual: delete agent, verify backing ACP session is also deleted
• Manual: verify agent names preserve original casing

NOTE

This relies on the changes in ambient-code/platform#855

[jsell-rh]

Review — TASK-052 AmbientSessionBackend (#63)

Overall: Solid implementation. The interface compliance is complete, error handling is consistent, and the 22 httptest-based tests give good coverage. PR is merged and all tests pass clean with -race.

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Strengths

Interface implementation is complete and correct

Compile-time checks at the top (var _ SessionBackend = (*AmbientSessionBackend)(nil) etc.) catch any missing methods at build time — good practice.

doRequest helper is clean

Single place for auth headers, Content-Type, and request construction. All methods delegate through it correctly.

KillSession gracefully handles 404

Treating 404 as success is correct — the session is gone either way, which is the goal.

runningOrIdle fallback is safe

Falling back to SessionStatusRunning on any error means the liveness checker won't incorrectly mark a session as idle when we can't reach the runs endpoint.

waitForRunning select pattern is correct

Using time.After(2s) inside select{ctx.Done, ...} properly respects context cancellation during polling. No goroutine leak.

Available() caching is correct

30s TTL with mutex protects the cache correctly. Checking resp.StatusCode < 500 (accepting 4xx as available) is the right heuristic.

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Observations (no change needed)

CaptureOutput truncates at 200 chars per message — reasonable payload guard but may complicate debugging. Consider extracting const maxMessageLen = 200 so it's easy to adjust.

DiscoverSessions only surfaces running/pending — correct for live session matching; completed/failed are intentionally excluded.

InsecureSkipVerify nolint comment — appropriate for OpenShift dev clusters with self-signed certs; opt-in via config is the right design.

Tests — 22 httptest mock server tests cover all methods including status mapping, TTL caching, discovery, and polling. Testing through the HTTP layer is the right approach.

Verdict: Approved. No required changes.