[CheckPickerUpper]

Linked issue

Closes #23

Observable behavior

• Project discovery now starts from recognized Roblox service directories and derives module side, role, and DataModel output path from that layout.
• Existing Luau and Roblox model assets are retained in the staged project tree; unknown services, illegal StarterPlayer placement, duplicate destinations, source/output collisions, and overlapping roots fail before generation.
• The lower-level one-module build command remains compatible.

Proof

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features --locked -- -D warnings
• cargo test --all-targets --locked (17 passed with pinned Luau tools)
• Manual valid-service/asset, legacy-layout rejection, and illegal-placement proofs

Scope

This PR is limited to Roblox-shaped project discovery, service-derived layout and role validation, retained project assets, deterministic output, and documentation. Events, remotes, and unrelated diagnostics are not changed.

[github-actions]

Visual recap — skipped

The visual recap job did not run for this pull request. This is informational only and does not block the PR.

Recap skipped for 14963d9: missing required recap label (visual-recap).