Add Taskfile for unified dev workflow across all components (#6080)

## Add Taskfile for unified dev workflow

### Summary
- Introduces [Taskfile](https://taskfile.dev/) as the single CLI entry
point for all development workflows across backend, frontend, engine,
Docker, and desktop
- ~80 tasks organized into 6 namespaces: `backend:`, `frontend:`,
`engine:`, `docker:`, `desktop:`, plus root-level composites
- All CI workflows migrated to use Task
- Deletes `engine/Makefile` and `scripts/build-tauri-jlink.{sh,bat}` —
replaced by Task equivalents
- Removes redundant npm scripts (`dev`, `build`, `prep`, `lint`, `test`,
`typecheck:all`) from `package.json`
- Smart dependency caching: `sources`/`status`/`generates`
fingerprinting, CI-aware `npm ci` vs `npm install`, `run: once` for
parallel dep deduplication

### What this does NOT do
- Does not replace Gradle, npm, or Docker — Taskfile is a thin
orchestration wrapper
- Does not change application code or behavior

### Install
```
npm install -g @go-task/cli    # or: brew install go-task, winget install Task.Task
```

### Quick start
```
task --list       # discover all tasks
task install      # install all deps
task dev          # start backend + frontend
task dev:all      # also start AI engine
task test         # run all tests
task check        # quick quality gate (local dev)
task check:all    # full CI quality gate
```

### Test plan
- [ ] Install `task` CLI and run `task --list` — verify all tasks
display
- [ ] Run `task install` — verify frontend + engine deps install
- [ ] Run `task dev` — verify backend + frontend start, Ctrl+C exits
cleanly
- [ ] Run `task frontend:check` — verify typecheck + lint + test pass
- [ ] Run `task desktop:dev` — verify jlink builds are cached on second
run
- [ ] Verify CI passes on all workflows

---------

Co-authored-by: James Brunton <jbrunton96@gmail.com>

.taskfiles/engine.yml

@@ -0,0 +1,124 @@
+version: '3'
+
+tasks:
+  install:
+    desc: "Install engine dependencies"
+    run: once
+    cmds:
+      - uv python install 3.13.8
+      - uv sync
+    sources:
+      - uv.lock
+      - pyproject.toml
+    status:
+      - test -d .venv
+
+  prep:
+    desc: "Set up engine .env from template"
+    deps: [install]
+    cmds:
+      - uv run scripts/setup_env.py
+    sources:
+      - scripts/setup_env.py
+      - config/.env.example
+    generates:
+      - .env
+
+  run:
+    desc: "Run engine server"
+    deps: [prep]
+    ignore_error: true
+    dir: src
+    env:
+      PYTHONUNBUFFERED: "1"
+    cmds:
+      - uv run uvicorn stirling.api.app:app --host 0.0.0.0 --port 5001
+
+  dev:
+    desc: "Start engine dev server with hot reload"
+    deps: [prep]
+    ignore_error: true
+    dir: src
+    env:
+      PYTHONUNBUFFERED: "1"
+    cmds:
+      - uv run uvicorn stirling.api.app:app --host 0.0.0.0 --port 5001 --reload
+
+  lint:
+    desc: "Run linting"
+    deps: [install]
+    cmds:
+      - uv run ruff check .
+
+  lint:fix:
+    desc: "Auto-fix lint issues"
+    deps: [install]
+    cmds:
+      - uv run ruff check . --fix
+
+  format:
+    desc: "Auto-fix code formatting"
+    deps: [install]
+    cmds:
+      - uv run ruff format .
+
+  format:check:
+    desc: "Check code formatting"
+    deps: [install]
+    cmds:
+      - uv run ruff format . --diff
+
+  typecheck:
+    desc: "Run type checking"
+    deps: [install]
+    cmds:
+      - uv run pyright . --warnings
+
+  test:
+    desc: "Run tests"
+    deps: [prep]
+    cmds:
+      - uv run pytest tests
+
+  fix:
+    desc: "Auto-fix lint + format"
+    cmds:
+      - task: lint:fix
+      - task: format
+
+  check:
+    desc: "Full engine quality gate"
+    cmds:
+      - task: typecheck
+      - task: lint
+      - task: format:check
+      - task: test
+
+  tool-models:
+    desc: "Generate tool_models.py from frontend TypeScript defs"
+    deps: [install]
+    cmds:
+      - uv run python scripts/generate_tool_models.py --output src/stirling/models/tool_models.py
+      - task: fix
+
+  clean:
+    desc: "Clean build artifacts"
+    cmds:
+      - task: '{{if eq .OS "Windows_NT"}}clean-windows{{else}}clean-unix{{end}}'
+
+  clean-unix:
+    internal: true
+    desc: "Clean build artifacts"
+    cmds:
+      - rm -rf .venv data logs output
+
+  # On Windows, use PowerShell as bash failed to delete some dependencies
+  clean-windows:
+    internal: true
+    desc: "Clean build artifacts"
+    ignore_error: true
+    cmds:
+      - powershell rm -Recurse -Force -ErrorAction SilentlyContinue .venv
+      - powershell rm -Recurse -Force -ErrorAction SilentlyContinue data
+      - powershell rm -Recurse -Force -ErrorAction SilentlyContinue logs
+      - powershell rm -Recurse -Force -ErrorAction SilentlyContinue output