C3: Tutorial setup — mode switch + project scaffold (overture stage 7)

[jeonghun-jj-lee]

Important

Problem — The tutorial needs a real Research Project to work in and a moment that teaches the mode system. Nothing today scaffolds a project during onboarding or demonstrates the plan→research switch.
Approach — Add a tutorial_setup stage to the score: narrate and perform the plan→research mode switch (spotlighting the posture indicator), scaffold the bundled unicycle Research Project template to ~/amicode-tutorial/, then spotlight the file tree and explain the project layout.
Scope — in: the tutorial_setup stage in SCORE.md, the scaffold-to-~/amicode-tutorial/ action, the posture + file-tree highlights · out: the three tutorial-loop stages, the scripts themselves (bundled in F3), the tour-target definitions (F2).

Acceptance Criteria

• The score's tutorial_setup stage switches the session from plan to research mode with a Tour · Posture narration
• The stage scaffolds the bundled template to ~/amicode-tutorial/ with research-project.toml, environments/, experiments/ (the three scripts), ledger/, and README
• A Tour · File tree narration explains the project layout after scaffolding
• Re-running onboarding does not error if ~/amicode-tutorial/ already exists (idempotent scaffold)
• Score lint passes

Testing Decisions

Extends score-lint coverage for the new stage. Add an assertion (unit-level, on the scaffold helper if one is extracted, else a documented manual step in the score) that scaffolding an existing target directory is idempotent. Header→selector for Tour · Posture and Tour · File tree reuses the tour-target contract test (depends on those anchors existing — see blocker F2).

Key Decisions

• The mode switch is a teaching moment, narrated explicitly ("watch the indicator change").
• Scaffold target is ~/amicode-tutorial/ (persists after onboarding for later reference), copied from the F3 template.
• Idempotent scaffold so a resumed or repeated onboarding is safe.

Constraints & Invariants

• The scaffold must not overwrite user edits if the tutorial dir already exists.
• Tour · Posture and Tour · File tree require the F2 anchors; experiments/ content requires the F3 scripts.

Prior Art

• The research mode bundle (posture indicator, mode switch mechanism)
• The F3 tutorial template and script layout
• The score body's existing action-narration patterns

Source

Part of #1160 · Blocked by #1166 · Blocked by #1162 · Blocked by #1163