feat(domain): integrate coasts dev server with feature flag and coastfile auto-generation

[arielshad]

Summary

• Add coastsDevServer feature flag across the full stack: TypeSpec model, SQLite migration, settings mapper, feature flags state, web UI toggle, and context defaults
• Implement ICoastsService output port interface with methods for prerequisite checks, build/run/stop lifecycle, coast instance lookup, and Coastfile auto-generation via AI agent system
• Implement CoastsService infrastructure service wrapping the coast CLI binary via child_process.spawn with proper error handling, timeouts, and subprocess safety
• Add dev-server branching logic: when the flag is enabled, check prerequisites, auto-generate Coastfile if missing, and start Next.js via coast run instead of bare next()
• Add coasts-dev-server.ts module with startCoastsDevServer() and shutdownCoasts() for clean separation of Coasts-mode startup/shutdown
• Add dev:coasts convenience script to package.json
• Register CoastsService in the DI container
• Comprehensive test coverage: 30 unit tests for CoastsService, 16 tests for coasts dev-server module, 12 integration tests for dev-server branching logic

What This Enables

When users enable the coastsDevServer feature flag, the Shep dev server uses Coasts for containerized runtime isolation per worktree. Each worktree gets its own isolated dev server instance with dedicated ports, volumes, and services — enabling true parallel feature development without port conflicts or shared state.

If a target repo lacks a Coastfile, Shep auto-generates one by running coast installation-prompt to obtain the official generation prompt, then passing it to the AI agent system to produce a tailored Coastfile based on the repo's actual structure.

Architecture

• Clean Architecture: ICoastsService interface in application layer, CoastsService implementation in infrastructure layer
• Feature flag pattern: follows established pattern with TypeSpec, SQLite migration, settings mapper, flag context, and UI toggle
• Agent resolution: Coastfile generation flows through IAgentExecutorProvider per mandatory agent resolution rule
• DI registration: CoastsService registered as ICoastsService token in the DI container

Evidence

Evidence	Description
	Coasts Dev Server toggle in Feature Flags settings
	Full settings page with integrated flag
CoastsService unit tests	30 tests passing — prerequisite checks, build, run, stop, checkout, lookup, isRunning, hasCoastfile, getInstallationPrompt, generateCoastfile
Coasts dev-server module tests	16 tests passing — full flow, prerequisite failures, Coastfile generation, log prefix, error handling
Dev-server branching integration tests	12 tests passing — prerequisite ordering, failure handling, build/run sequencing, Coastfile detection
Full test suite	382 test files, 5080 tests (4559 unit + 521 integration), ALL passing

Test plan

• Build compiles without errors (pnpm build)
• All 4559 unit tests pass (pnpm test:unit)
• All 521 integration tests pass (pnpm test:int)
• Lint passes with zero warnings (pnpm lint:fix)
• Feature flag defaults to false (no behavior change for existing users)
• CI passes on all workflow runs

🤖 Generated with Claude Code

[github-actions]

Dev Release Published

Artifact	Version	Install
npm	1.135.2-pr437.64c56e0	npm install -g @shepai/cli@1.135.2-pr437.64c56e0

---

_{Published from commit d7232e2 | View CI}

[github-actions]

Dev Release Published

Artifact	Version	Install
npm	1.136.0-pr437.9f802f1	npm install -g @shepai/cli@1.136.0-pr437.9f802f1

---

_{Published from commit ad3b11a | View CI}