F10 #31: render resolved proposals inline at their anchor block

In the F10 review preview, renderReview now emits each pending proposal whose
anchor resolves as a cw-proposal block immediately after the current-side block
its anchorStart falls in — answering "what is Claude proposing, and where?" by
position — instead of appending all proposals as trailing blocks. Proposals in
the same block are ordered by anchorStart then id (deterministic, INV-33); a
proposal whose anchor doesn't resolve (or precedes all blocks) still trails as a
cw-proposal-unanchored block, never dropped (INV-34).

This implements the inline-at-anchor placement the graduated F10 Solution Design
already specified (coauthoring-interactive-review.md §2/§6.2); the trailing-block
behavior shipped in #29 was a recorded v1 deferral.

Unit: mid-document placement, two proposals in distinct blocks, same-block
ordering determinism, anchored-before-trailing, mixed-set determinism.
E2E: the F10 propose test now asserts the proposal renders before the following
block (in place); accept still lands + clears.

194 unit + 51 E2E green; typecheck clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

test/e2e/suite/f10Review.test.ts

@@ -104,6 +104,11 @@ suite("F10 interactive review (host E2E — preview is the single review surface
     const html = api.trackChangesPreviewController.renderHtmlFor(key);
     assert.ok(html.includes(`data-proposal-id="${id}"`), "the preview renders the proposal block by id");
     assert.match(html, /class="cw-actions"/, "the proposal block carries ✓/✗ actions");
+    // #31: the proposal renders INLINE at its anchor (right after T1's block), not
+    // trailing the whole document — so it appears BEFORE the following T2 block.
+    const pIdx = html.indexOf(`data-proposal-id="${id}"`);
+    const t2Idx = html.indexOf("second claude target");
+    assert.ok(t2Idx >= 0 && pIdx < t2Idx, "the proposal renders in place, before the following block (#31)");
     // INV-10: proposing never touches the document.
     assert.ok(doc.getText().includes(T1), "document unchanged by propose");
   });