Refactor metadata fetch and reorganize docs/workflows

.github/copilot-instructions.md

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+# Copilot Instructions for `goark/ml`
+
+## Project purpose
+
+`ml` is a CLI and library that fetches metadata from web pages and formats links
+as markdown/wiki/html/csv/json output.
+
+## Design principles
+
+- Keep CLI behavior simple and deterministic.
+- Keep output formatting stable for all supported styles.
+- Reuse `github.com/goark/webinfo` for metadata extraction.
+- Preserve compatibility of exported symbols when possible.
+
+## Error handling
+
+- Use `github.com/goark/errs` for internal error handling.
+- Prefer `errs.Wrap`, `errs.Join`, and `errs.WithContext`.
+- Keep `errors.Is` compatibility for callers.
+- Keep sentinel errors stable (`ErrNullPointer`, `ErrNoImplement`, `ErrInvalidRequest`).
+- Include useful context keys such as `url`, `style`, and `path`.
+
+## Fetch behavior
+
+- Fetch and metadata parsing are delegated to `github.com/goark/webinfo`.
+- Keep `makelink.New` mapping behavior stable:
+  - `Link.URL <- Webinfo.URL`
+  - `Link.Location <- Webinfo.Location`
+  - `Link.Canonical <- Webinfo.Canonical`
+  - `Link.Title <- Webinfo.Title`
+  - `Link.Description <- Webinfo.Description`
+- Preserve URL fallback behavior for output rendering:
+  - title fallback: `Title` -> `URL`
+  - URL fallback: `Canonical` -> `Location` -> `URL`
+
+## Output style behavior
+
+- Keep style names and output formats stable:
+  - `markdown`: `[title](url)`
+  - `wiki`: `[url title]`
+  - `html`: `<a href="url">title</a>`
+  - `csv`: escaped CSV fields in fixed order
+  - `json`: JSON encoded `Link`
+- Keep CSV quote escaping behavior unchanged.
+
+## Coding style
+
+- Write idiomatic Go with straightforward control flow.
+- Avoid unnecessary dependencies.
+- Keep comments concise and in English.
+
+## Testing and validation
+
+- Add or update tests for behavior changes.
+- Prefer local validation with Taskfile targets:
+  - `task test`
+  - `task govulncheck`
+
+## Documentation
+
+- Keep `README.md` aligned with actual CLI and exported API behavior.
+- Keep examples concise and runnable.
+
+## Release process
+
+- Create release tags from `master`.
+- Use semantic versioning tags in `vMAJOR.MINOR.PATCH` format.
+- Ensure repository is clean and synced before tagging.
+
+Release steps:
+
+1. Ensure `master` is up to date.
+2. Create annotated tag:
+  - `git tag -a vX.Y.Z -m "Release vX.Y.Z"`
+3. Push tag:
+  - `git push origin vX.Y.Z`
+4. Wait for the `build` workflow triggered by the tag push to complete.
+
+Verification steps:
+
+- Check tag exists:
+  - `git tag -l "vX.Y.Z"`
+- Check `build` workflow result for the tag run (success/failure).
+- Check release exists:
+  - `gh release view vX.Y.Z`
+- Check generated release notes are present in the release page.

.github/workflows/ci.yml

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+name: ci
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+
+permissions:
+  contents: read
+
+jobs:
+  test-and-lint:
+    name: lint and test
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: actions/setup-go@v6
+        with:
+          go-version-file: go.mod
+          cache-dependency-path: go.sum
+
+      - name: golangci-lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: latest
+          args: --enable gosec
+
+      - name: Test module
+        run: go test -shuffle on ./...
+
+  govulncheck:
+    name: govulncheck
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Run govulncheck
+        uses: golang/govulncheck-action@v1
+        with:
+          go-version-file: go.mod
+          go-package: ./...
+          repo-checkout: false

.github/workflows/codeql.yml

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+name: CodeQL
+
+on:
+  push:
+    branches:
+      - master
+  pull_request:
+    branches:
+      - master
+  schedule:
+    - cron: "0 20 * * 0"
+
+permissions:
+  actions: read
+  contents: read
+  security-events: write
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: go
+
+      - name: Autobuild
+        uses: github/codeql-action/autobuild@v3
+
+      - name: Perform CodeQL analysis
+        uses: github/codeql-action/analyze@v3