fix(docs): make doc tree folders toggle open/closed

[ajianaz]

Problem

Parent folders in the document tree could not be expanded/collapsed. Clicking the chevron changed nothing.

Root cause — Svelte 5 reactivity bug

expandedIds is a \$state Set and the tree snippet reads it via {@const expanded = expandedIds.has(id)}. The toggle handlers mutated the Set in place (.add()/.delete()) and then reassigned the same reference (expandedIds = expandedIds). In Svelte 5 this does not re-run {@const} reads, so the {#if expanded} block never updated — the Set changed, the UI didn't.

This is independent of the earlier /doc/list limit fix (#159). Even with full children loaded, the toggle was dead.

Fix

Use immutable updates everywhere expandedIds / childrenCache change — build a new Set/Map and reassign the new reference. Svelte 5 reliably re-renders the snippet on a reference change.

Sites:

• toggleNode, expandPathToDoc, selectDoc → expandedIds = new Set(...)
• loadChildren → childrenCache = new Map(...)

Proof

Added a regression test (TreeRepro.svelte + set-reactivity.test.ts) that reproduces the snippet pattern. It fails with the old in-place + same-ref reassign pattern and passes with the immutable update.

Checks

• vitest — 61 passed (incl. new regression test) ✅
• svelte-check — 0 errors ✅
• npm run build ✅

[github-actions]

🔍 Cora AI Code Review

⚠️ Review recommended — warnings found.

🟡 Warning (1)

• unknown:? — Cora AI review could not complete: failed to parse LLM JSON response: parse failed (original: EOF while parsing a value at line 1 column 0, after repair: EOF while parsing a value at line 1 column 0). Review was skipped; no code quality issues were found by the automated check.

---

Review powered by cora-cli · BYOK · MIT