Story-2035: light + full presets + toolbar + per-preset round-trip

Story-2024 laid the keystone: markdown installed under EditableSurface and a preset seam, shipping only plain. This story fills the seam — it makes light and full reachable, adds the formatting bubble-menu toolbar, and proves markdown round-trip identity per preset. Adding a tier stayed one entry in resolvePreset, never a new editor. The Brief is untouched — it stays on plain.

What landed

• resolvePreset now resolves plain | light | full to { extensions, contentType, toContent, toValue, toolbar }. plain is unchanged (JSON doc, literal text, no toolbar). light/full load and save as markdown (contentType: "markdown") and carry a toolbar config.
• Preset subsets are enforced in the schema, not just the toolbar. light enables only bold, italic, link; every block node and other mark is disabled. full adds #/##/### headings, -/1. lists, and > blockquotes. A construct outside the subset can never be produced, so the serializer can never emit something the round-trip won't preserve.
• New EditableSurfaceToolbar (editable-surface-toolbar.tsx) — a @tiptap/react BubbleMenu that floats over the selection with one icon button per enabled action. It mounts only when the resolved strategy has a toolbar (i.e. never for plain) and the surface is editable. Each button toggles a mark/node via a focused command chain.
• A format action trips the save icon. The substrate's dirty check (from Story-2024) compares getMarkdown() to the committed baseline. Toggling bold on a selection mutates the doc → the markdown diverges → onDirtyChange(true) fires, even though no characters were typed. That divergence is proved headlessly in the test.

How a markdown preset loads without an editor in hand

plain builds its ProseMirror doc directly in toContent. A markdown preset can't — parsing needs the editor's markdown manager, which doesn't exist at useEditor init. The seam that avoids re-plumbing the primitive: the strategy exposes a contentType, and toContent for a markdown preset just returns the raw string. Every setContent call site (init, Escape-revert, external-value sync) passes { contentType: strategy.contentType }, so TipTap parses markdown at set-time. toValue is getMarkdown() with a trailing newline stripped, so an untouched value doesn't spuriously trip dirty/save (the story's "modulo trailing-newline normalization").

Round-trip identity, tested as a fixpoint

Rather than pin brittle exact serializer output, each preset's round-trip test loads a value, saves it (first), loads that and saves again (second), and asserts second === first — a stable fixpoint — plus that the preset's promised formatting survived. So light preserves **bold**, *italic*, and [text](url) but drops a stray # to inline text; full preserves headings, lists, and blockquotes.

Files

• src/components/shared/editable-surface-preset.ts — light/full strategies, contentType, and per-preset toolbar config.
• src/components/shared/editable-surface-toolbar.tsx — new: the bubble-menu formatting toolbar.
• src/components/shared/editable-surface.tsx — threads contentType through setContent, renders the toolbar + block-formatting styles for formatting presets.
• src/components/shared/editable-surface-preset.test.ts — per-preset round-trip identity, toolbar config, and the format-trips-dirty mechanism.
• src/components/shared/editable-surface.test.tsx — plain carries no toolbar button.
• src/components/shared/editable-surface.stories.tsx — new LightPreset and FullPreset stories.
• messages/en.json / messages/hi.json — EditableSurface.toolbar action labels (both locales).

No Brief regression

preset still defaults to "plain"; the Brief data fields pass no preset and behave exactly as before. light/full are reachable but not yet wired into any Brief field — that flip is a later per-field prop change (RFD §6 step 4), out of this story's scope.

Deliberately deferred (not this story)

• Flipping any Brief field to light — a one-prop change gated on the frame-contract story (RFD §3a).
• The Draft Workspace full consumer against the document entity (RFD §3b).
• Link entry uses window.prompt for the URL; a styled popover is a later UX pass. full's later tier (tables, footnotes) is out of scope per RFD §7.
• No pnpm codegen run; no wire-contract change.

Verification

pnpm lint (clean, one pre-existing unrelated warning), pnpm build (green, TypeScript passes), and the full pnpm test suite (1009 tests, incl. the per-preset round-trip and toolbar tests) all pass. The LightPreset / FullPreset Storybook stories demonstrate the bubble-menu toolbar on selection, the dirty flag tripping on a formatting-only edit, and the markdown value round-tripping.