refactor(cm): build table and image block widgets from one structural block contract

src/webview/cm/bounded-recompute.ts

@@ -1,15 +1,8 @@
-// Small pure leaf helpers shared by the block-widget StateFields that maintain
-// their DecorationSet / model list with a changed-range-bounded recompute
-// (image/image-field.ts, table/table-field.ts, table/table-skeleton.ts — see
-// PERF.md). These were byte-identical copies in each file; they live here as ONE
-// implementation so the copies cannot drift.
-//
-// SCOPE: only the small, self-contained leaf helpers are shared. A full
-// `defineBlockWidgetField` FACTORY over `buildAll` was deliberately REJECTED as
-// leaky — the table field's global ordinal makes bounding it genuinely different
-// from the image field's widget-reuse — and is gated on a future third consumer
-// (the list block widget). See the recorded decision in
-// .claude/docs/TODO-archive.md. Do NOT grow this module into that factory.
+// Small pure leaf helpers shared by the changed-range-bounded StateFields. The
+// structural block widgets (table, image) use them through the contract module
+// structural-blocks.ts, which owns the bounded update itself; this module stays the
+// home of the leaf helpers only, so the field logic lives in exactly one place
+// (structural-blocks.ts) and the helpers cannot drift between consumers.
 //
 // The three fold-gutter fields (fold/index.ts), the callout marker-conceal field
 // (decorations/callout-marker-conceal.ts), and fenced-code collapse
@@ -71,8 +64,9 @@ export function intersects(intervals: readonly Interval[], from: number, to: num
 }
 
 /** True iff any range in `selection` overlaps the inclusive `[from, to]` line
- *  interval. `from`/`to` are line-aligned by the block fields' `buildAll`, so
- *  the closed interval catches caret-at-boundary cases half-open would miss.
+ *  interval. `from`/`to` are line-aligned by each structural block's `build`
+ *  (structural-blocks.ts `validRange`), so the closed interval catches
+ *  caret-at-boundary cases half-open would miss.
  *  A `SelectionRange` is structurally `{ from, to }`, so this is just
  *  `intersects` over the selection's ranges. */
 export function lineRangeOverlapsSelection(

src/webview/cm/fenced-code/fenced-code-collapse.ts

@@ -17,7 +17,6 @@
 // zone is non-atomic, and reachability is the auto-expand's job — not the generic
 // blockZoneArrowKeymap's.
 
-import { syntaxTreeAvailable } from "@codemirror/language";
 import type { EditorState, Transaction } from "@codemirror/state";
 import type { DecorationSet } from "@codemirror/view";
 import { type Interval, lineExpandWithNeighbours, mergeIntervals } from "../bounded-recompute.js";
@@ -29,6 +28,7 @@ import {
 } from "../collapse/line-collapse-field.js";
 import { leadingFrontmatterEnd } from "../frontmatter/detect.js";
 import { linkReferenceRisk } from "../link-reference-risk.js";
+import { frontierIncomplete } from "../structural-guard.js";
 import { fencedCollapseTarget } from "./fenced-code-collapse-state.js";
 import { FencedCollapseToggleWidget } from "./fenced-code-collapse-widget.js";
 
@@ -195,11 +195,12 @@ function computeExtendedSpan(tr: Transaction): Interval[] {
 }
 
 // The fenced policy, unchanged: GF structural edit or a top-level boundary move → full;
-// an incomplete parse → full (G2 frontier); otherwise changed lines ±1 ∪ selection lines.
+// an incomplete parse frontier → full; otherwise changed lines ±1 ∪ selection lines.
 //
-// The frontier gate (an incomplete parse can reveal nodes outside the span) is spelled out
-// here, and the structural-reparse fallback is deliberately NOT part of this condition, the
-// way it is in the fields that import ../structural-guard.js: `touchesStructural` /
+// The frontier gate (an incomplete parse can reveal nodes outside the span, and records
+// built over a partial snapshot miss blocks beyond it) is the shared `frontierIncomplete`,
+// but the structural-reparse half of `requiresFullBoundedRebuild` is deliberately NOT part
+// of this condition, the way it is in the other bounded fields: `touchesStructural` /
 // `topLevelBoundaryRisk` above already return "full" before the gate is reached. That guard
 // is narrower than the shared predicate on purpose — this field's hot path is editing INSIDE
 // a code fence, where a `#` comment or a `___` line must stay bounded; ../structural-guard.ts's
@@ -221,7 +222,7 @@ const fencedCollapseSpec: LineCollapseSpec<null> = {
     leadingFrontmatterEnd(tr.startState) !== leadingFrontmatterEnd(tr.state) ||
     touchesStructural(tr) ||
     topLevelBoundaryRisk(tr, prevBlocks) ||
-    !syntaxTreeAvailable(tr.state, tr.state.doc.length)
+    frontierIncomplete(tr)
       ? "full"
       : computeExtendedSpan(tr),
 };