fix(search_code): fuzzy mid-word matching + Luau/fuzzy live test coverage

Address the remaining real defects from the Luau/cs test reports. The wrapper-
level findings (dash-leading queries, context flag, no-match message, empty
query, path-is-file) were already fixed in earlier commits and verified through
the tool; the two genuinely-open items were engine-level, plus a test-coverage
gap (the patch-dependent behaviors were only exercised by live tests that
skip without a cs binary).

- Engine fix (docker/cs/fuzzy-distance.patch): cs's fuzzy `term~N` only scanned
  same-length windows, so it matched substitutions but never mid-word
  insertions/deletions — e.g. `computSlipAngle~1` (a dropped 'e') failed to find
  `computeSlipAngle`, contradicting cs's own "within 1 or 2 distance" docs.
  Now scan windows of length termLen±maxDist (true Levenshtein) and keep the
  best per offset. Updates one pre-existing cs test that encoded the buggy
  substitution-only behaviour and adds mid-word insert/delete cases. Passes
  cs's pkg/search + pkg/ranker suites; builds clean against the pinned commit.
- Provisioning: apply the new patch everywhere the Luau patch is applied —
  Dockerfile, Dockerfile.dev, packaging/PKGBUILD build() — so every install
  path (Docker bin/up, native code-search package via bin/service install)
  ships both patches.
- Tests: add skip-gated live tests for Luau declaration detection (function /
  local function / type / export type), only=usages exclusion, the Luau
  language tag, and fuzzy mid-word matching. New capability probes
  (findLuauCapableCs / findFuzzyCapableCs) run these only on a cs that actually
  has each patch and skip (never fail) on an unpatched/absent binary. Default
  suite: 600 pass / 12 skip; with a both-patched cs: 612 pass / 0 skip.
- Docs: UPSTREAM_CS_FUZZY_BUG.md documents the unreported upstream defect for a
  potential boyter/cs PR; CS_ARTIX_DEPLOY.md updated to reflect that
  sync-dispatch.sh now ships the code-search package (carrying both patches).

biome + tsc (core/api/frontend) + svelte-check all green.

1 files changed, 4 insertions, 1 deletions

diff --git a/Dockerfile.dev b/Dockerfile.dev
index 52b1aa2..94d30fb 100644
--- a/Dockerfile.dev
+++ b/Dockerfile.dev
@@ -1,16 +1,19 @@
 # --- cs (code spelunker) builder ---
 # Builds a patched, statically-linked `cs` binary for the search_code tool.
 # Pinned to the v3.1.0 commit for reproducibility; the patch adds Luau
-# declaration support (see docker/cs/luau-declarations.patch). cs vendors its
+# declaration support and corrects fuzzy edit-distance matching (see
+# docker/cs/luau-declarations.patch and docker/cs/fuzzy-distance.patch). cs vendors its
 # dependencies, so the `go build` step is offline after the clone.
 FROM golang:1.25-bookworm AS cs-builder
 ARG CS_COMMIT=697e0bf194bbc7a4a877e5170c70618989fc92e7
 WORKDIR /build
 COPY docker/cs/luau-declarations.patch /tmp/luau-declarations.patch
+COPY docker/cs/fuzzy-distance.patch /tmp/fuzzy-distance.patch
 RUN git clone https://github.com/boyter/cs.git src \
 	&& cd src \
 	&& git checkout "${CS_COMMIT}" \
 	&& git apply /tmp/luau-declarations.patch \
+	&& git apply /tmp/fuzzy-distance.patch \
 	&& CGO_ENABLED=0 go build -mod=vendor -ldflags="-s -w" -o /usr/local/bin/cs . \
 	&& /usr/local/bin/cs --version