Add ao spawn + ao project add (spawn a real worker end-to-end)

[yyovil]

Summary

Closes the last gap to a live ao spawn: a registered project can now spawn a real worker agent (claude-code/codex) in a zellij pane, end-to-end from the CLI. Stacked on #65 (the agent-adapter + session-manager/daemon wiring this builds on).

What's new

• DB-backed RepoResolver — the daemon resolves a project's on-disk repo path from the projects table, replacing the empty StaticRepoResolver{} that failed every lookup. A registered project is now spawnable.
• Server-side branch defaulting — an empty spawn branch becomes ao/<session-id> (unique per session; gitworktree can't add a worktree on a branch already checked out, e.g. main).
• ao project add --path <repo> — register a local git repo (POST /api/v1/projects).
• ao spawn --project <id> [--harness] [--branch] [--prompt] [--issue] — spawn a worker (POST /api/v1/sessions); harness defaults to the daemon's AO_AGENT.
• Shared postJSON daemon client (run-file port lookup + API error envelope surfacing).

Demo flow

ao start
ao project add --path /path/to/a/git/repo --id demo
ao spawn --project demo --harness claude-code --prompt "say hi"
zellij attach demo-1     # watch Claude run in the pane

Requires zellij and the claude/codex binary on PATH.

Tests

• projectRepoResolver resolves a registered project / errors on an unregistered one.
• session_manager defaults the branch to ao/<id> and keeps an explicit branch.
• ao spawn/ao project add reject missing required flags before any network call.
• go build / go vet / golangci-lint (0 issues) / gofmt clean.

Base is codex/agents-plugin for a clean stacked diff. After #65 merges, retarget this PR to main.

[greptile-apps]

Greptile Summary

This PR wires up the full ao spawn and ao project add end-to-end flow: a DB-backed projectRepoResolver replaces the stub StaticRepoResolver, server-side branch defaulting ensures unique per-session worktrees, and two new CLI commands (spawn, project add) drive the daemon over a shared postJSON client.

• projectRepoResolver resolves registered projects from the SQLite projects table, wrapping lookup failures in ErrProjectNotResolvable so writeSessionError maps them to HTTP 400. The archived-project and missing-path guard clauses make failures explicit rather than opaque.
• Branch defaulting in session_manager.Spawn computes ao/<session-id> before the workspace is created, ensuring gitworktree never tries to add a worktree on a branch that's already checked out.
• CLI commands (spawn, project add) define local request/response structs and share the postJSON client; a DTO-drift E2E test exercises the real HTTP round-trip through the actual router to detect silent JSON field-name divergence.

Confidence Score: 5/5

Safe to merge — all critical paths (repo resolution, branch defaulting, error mapping) are correct and covered by tests.

The three core behavioural changes — DB-backed repo resolution, per-session branch defaulting, and the CLI commands — are all wired together correctly. Error wrapping with %w is consistent throughout so the ErrProjectNotResolvable to HTTP 400 mapping works end-to-end. The DTO-drift E2E test exercises the real HTTP router, catching any JSON field-name divergence at test time rather than at runtime. The zellij socket-dir fix is well-guarded (MkdirAll + warn-not-abort) and the socket-path budget test verifies the constraint quantitatively.

No files require special attention.

Important Files Changed

Filename	Overview
backend/internal/cli/client.go	New shared postJSON helper: reads run-file for port, validates daemon liveness, sets a 2-minute client timeout on a copy of the injected HTTP client, and surfaces the API error envelope.
backend/internal/cli/spawn.go	New ao spawn command: validates --project before any network call, POSTs spawnRequest, and prints a copy-pasteable attach hint using zellij.SessionName and zellij.DefaultSocketDir.
backend/internal/daemon/lifecycle_wiring.go	Replaces StaticRepoResolver with projectRepoResolver backed by SQLite; guards archived projects and missing paths, wrapping all failures in ErrProjectNotResolvable for HTTP 400 mapping.
backend/internal/session_manager/manager.go	Branch defaulting added before workspace.Create: defaults to ao/{session-id}; ws.Branch (not the local variable) is persisted in metadata.
backend/internal/service/project/service.go	validateProjectID now rejects embedded .. to prevent invalid git branch names surfacing as opaque 500s at spawn time.
backend/internal/adapters/runtime/zellij/zellij.go	DefaultSocketDir and SessionName exported; fixes macOS unix socket path budget overflow for long session IDs.

_{Reviews (6): Last reviewed commit: "fix(cli,daemon): address review findings..." | Re-trigger Greptile}

[Copilot]

Pull request overview

This PR closes the loop for an end-to-end “spawn a real worker” flow by adding CLI commands to register a local repo as a project and then spawn a worker session against that registered project. On the daemon side, it replaces the prior always-failing static repo resolver with a DB-backed resolver and adds server-side branch defaulting to ensure git worktree creation succeeds when the user doesn’t specify a branch.

Changes:

• Default session worktree branch to ao/<session-id> when none is provided during spawn.
• Wire a DB-backed RepoResolver that resolves a project’s repo path from the projects table.
• Add CLI commands ao project add and ao spawn, plus a shared postJSON client helper and basic “missing required flags” tests.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
backend/internal/session_manager/manager.go	Defaults spawn branch to a unique per-session branch before creating the worktree.
backend/internal/session_manager/manager_test.go	Adds unit tests for default-branch behavior and preserving explicit branches.
backend/internal/daemon/lifecycle_wiring.go	Switches gitworktree wiring to a DB-backed repo resolver and implements projectRepoResolver.
backend/internal/daemon/wiring_test.go	Adds a resolver test ensuring registered projects resolve to repo paths and unregistered projects error.
backend/internal/cli/root.go	Registers new spawn and project commands on the CLI root.
backend/internal/cli/client.go	Adds shared postJSON helper for POST requests to the daemon API.
backend/internal/cli/spawn.go	Implements ao spawn command (POST /api/v1/sessions).
backend/internal/cli/spawn_test.go	Adds fast-fail tests for missing required flags (no network calls).
backend/internal/cli/project.go	Implements ao project add (POST /api/v1/projects).

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