Sightread — M0

Learn to read code. Paste Python, tap anything underlined, get an explanation calibrated to your level. This is the M0 milestone from docs/sightread-design-doc.md: the proof-of-interaction build — client-only, no backend, no accounts, no analytics.

Run it

npm install
npm run dev        # http://localhost:5173
npm test           # resolver fixture tests (node)
npm run pack:build # compile packs/py/src into packs/py/build/v0
npm run budget     # verify entry bundle stays inside the M1 app-shell budget
npm run build      # production build in dist/

What's here

Path	Role (design doc §10.1)
src/reader/	CodeMirror 6 read-only view, tap decorations, the margin-note card
src/parse/	web-tree-sitter lifecycle (wasm sources injectable: browser + node tests)
src/resolve/	T0 engine: selector compilation, match index, §6.2 resolution, guards, ~35-concept corpus
src/app/	shell, level control, paste panel, zustand store
packs/py/src/	M1 pack-source skeleton migrated from the M0 hardcoded corpus
public/packs/py/v0/	generated static pack served to the browser runtime
tools/compile-pack.mjs	dependency-free pack compiler for the current YAML-compatible source subset
public/*.wasm	tree-sitter core + Python grammar (official tree-sitter-python npm wasm)
docs/	design doc, metrics & decision spec, pack format & selector spec

Architecture notes

• The resolver implements the normative algorithm of the pack spec §6.2 (promotion stops → candidate chain → priority, then smallest span). The same match index drives decorations, so tappable and resolvable can't disagree (§6.6).
• Guards implemented: not_locally_bound (with the honest shadow card per I5), is_callee, inside, not_inside. Binding analysis is single-file best-effort by design (N2).
• The browser runtime loads the generated Python pack from public/packs/py/v0. The old hardcoded src/resolve/concepts.ts corpus remains only as the M0 migration source and resolver test fixture for now.
• Production builds register a small service worker that caches the app shell, built assets, WASM, and immutable /packs/py/v0 files after first load.
• The current corpus has also been migrated into packs/py/src/concepts/**/*.yaml. Rebuild generated pack artifacts with npm run pack:build; this writes ignored staging output to packs/py/build/v0 and served runtime output to public/packs/py/v0. Rerun the one-time migration from the old runtime corpus with npm run pack:migrate:m0.
• Level gates work end to end: try tapping the = in an assignment at "New to this" vs "Comfortable".

Known M0 shortcuts (intentional)

• CM6 + web-tree-sitter ship in the main JS chunk (~800 KB). The design doc's I3/I17 budgets apply from M1; fix is a dynamic import of the reader stack.
• No incremental reparse — the doc is read-only, so every code change is a full parse (fast at these sizes).
• Grammar wasm compatibility: use the wasm from the official tree-sitter-python npm package (currently 0.25.0). The tree-sitter-wasms package is built with tree-sitter-cli 0.20 and will not load under web-tree-sitter 0.26.
• expected_output fields and example-execution CI (pack spec §9.4) start at M1.

Exit criterion

A learner pastes a snippet and the tap-to-card loop feels magical on a phone browser.

Test on a real phone: npm run dev -- --host, then open the LAN URL.