build: add .claude/skills for updating llgo version

.claude/skills/update-llgo-version.md

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+---
+name: update-llgo-version
+description: Update the github.com/goplus/llgo dependency version across the llcppg project — Go module, CI workflows, and setup action. Use this skill whenever the user asks to bump, update, or upgrade the llgo version, or mentions changing the llgo dependency, even if they don't use the exact phrase "update llgo version".
+---
+
+# Update LLGo Version
+
+Update `github.com/goplus/llgo` to a new version across the entire project. Six files reference the llgo version and they all need to stay in sync.
+
+## Instructions
+
+Given a target version (e.g., `v0.14.0`):
+
+### Step 1: Detect the current version
+
+Read `go.mod` and note the current `github.com/goplus/llgo` version — you'll need it for the commit message.
+
+### Step 2: Update Go module dependency
+
+Use `go get` to update the module dependency, then tidy:
+
+```bash
+go get github.com/goplus/llgo@<target_version>
+go mod tidy
+```
+
+This updates both `go.mod` and `go.sum` automatically. Using `go get` is safer than manually editing `go.mod` because it resolves transitive dependencies correctly.
+
+### Step 3: Update CI workflow matrices
+
+Three workflow files have a `strategy.matrix.llgo` entry that pins the llgo version. Update each one:
+
+- `.github/workflows/go.yml` — line with `llgo: [...]`
+- `.github/workflows/end2end.yml` — line with `llgo: [...]`
+- `.github/workflows/gentest.yml` — line with `llgo: [...]`
+
+Replace the version in the `llgo` array, e.g., `llgo: [v0.14.0]`.
+
+### Step 4: Update the setup action default
+
+In `.github/actions/setup-llcppg/action.yml`, update the `default` value for the `llgo` input to match the new version.
+
+## Verification
+
+After making all changes, run these commands to confirm nothing is broken:
+
+```bash
+go mod tidy
+go build -v ./...
+go vet ./...
+go test -v ./config ./internal/name ./internal/arg ./internal/unmarshal
+```
+
+These are the fast unit tests. If they pass, the version bump is safe to commit.
+
+## Commit Convention
+
+```
+build(deps): bump github.com/goplus/llgo from <old_version> to <new_version>
+```
+
+Replace `<old_version>` with the version you noted in Step 1 and `<new_version>` with the target version.