fix(context): retain Unicode concepts and preserve upgrade notes

[xiehuanyi]

Concept slugs retain Unicode letters, digits and combining marks, with NFC normalization. Cyrillic, CJK, Arabic and Greek concepts keep their separate files and links; mixed-script names retain the words around URL instead of collapsing into one URL node.

Fixes #543 for the reported non-Latin and mixed-script name loss.

Upgrading the slug policy preserves human notes: an unambiguous old name transfers its notes to a new file, and every changed note file is backed up byte-for-byte under .cache/slug-upgrades/ before pruning. Formerly merged or already-existing targets retain a backup for manual reconciliation; reusing the old ASCII slug cannot attach a merged node's notes to a different concept.

Validation: both Unicode regressions fail before the slug fix. Three real legacy-upgrade cases cover unique notes, formerly merged names, ASCII slug reuse, exact backups and repeated rebuilds; all 38 context tests pass. Build and diff checks pass. The complete suite with test concurrency limited to four reports 1,361 passed / 1 existing skip; the first broad run hit an unrelated signup loopback-fetch failure, whose 16 tests pass in isolation. Independent review caught and verified the note migration fix.

This changes Unicode slug construction; the general ASCII punctuation-collision policy is outside this fix.

AI-assisted implementation and wording.

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[trailhq-graft]

🌱 graft blast radius

1 area changed → 2 areas can be affected. 2 dependent symbols, depth 2.
Tests: 1 area updated its tests.
Tag: @anirudhkumar-nanonets — 3 of 3 areas · @Frankie-Xu — Build Context · @shhdwi — Workspace CLI

flowchart TB
  A0(("Workspace CLI<br/>1 symbol"))
  A1(("Engine Initialization<br/>1 symbol"))
  classDef reached fill:#D9EDF3,stroke:#3AA7C9,stroke-width:1.5px,color:#0E313C;
  class A0,A1 reached;

Loading

Can be affected	Symbols	Nearest hop	Reached from
Workspace CLI	1	src/graph/workspace-cli.ts:L49-L70 buildChild — calls, depth 2	Build Context
Engine Initialization	1	src/engine.ts:L63-L73 init — calls, depth 1	Build Context

Who knows this code — 3 people across 3 areas

Area	Who knows it
Build Context · changed	@anirudhkumar-nanonets — 10 commits, last 18d ago · @Frankie-Xu — 5 commits, last 1mo ago
Workspace CLI · affected	@shhdwi — 3 commits, last 2mo ago · @anirudhkumar-nanonets — 2 commits, last 2mo ago
Engine Initialization · affected	@anirudhkumar-nanonets — 16 commits, last 2mo ago

Ownership is git history over each area's own files, weighted towards recent work (120-day half-life). Merge commits and bots are dropped, and you are dropped from your own PR. A name with no @ has no GitHub handle in its commit email — tag them by hand, or add a .mailmap entry. A suggestion from history, not a CODEOWNERS rule.

All 2 dependent symbols, grouped by area

Workspace CLI — 1 symbol in 1 file

• src/graph/workspace-cli.ts:L49-L70 — buildChild (calls, depth 2)

Engine Initialization — 1 symbol in 1 file

• src/engine.ts:L63-L73 — init (calls, depth 1)
  64: return buildContext(dir, {

Test signal per changed area — 1 ✓

Reached = a node under a test path has a resolved edge into the changed symbol. It undercounts anything called indirectly — through a CLI, a spawned process or a dynamic import — so read a low ratio as “look here”, never as a coverage gate.

• ✓ Build Context — 2 of 4 reached · 1 test file changed here: test/context.test.ts
  • not reached: key, legacy

4 test suites also reference this code

4 symbols, kept out of the diagram and the table so they cannot crowd out the areas a reviewer has to look at.

• test/context-checkpoint.test.ts
• test/context-only-dir.test.ts
• test/covers.test.ts
• test/utf16-source.test.ts

_{graft blast · origin/main...HEAD · depth 2 · 3 changed files}

Open the interactive graph → — click an area to see its dependent symbols at file:line.