Add /check-links skill for broken wiki-link detection

Read-only analysis skill that finds broken [[wiki-links]] by
extracting link targets from all markdown files and verifying
each target file exists via Glob. Groups broken links by source
file and suggests close matches for misspelled targets.

Handles edge cases: heading anchors, block references, aliases,
embedded images, template placeholders, and external links.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vault-template/.claude/skills/check-links/SKILL.md

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+---
+name: check-links
+description: Find broken wiki-links in the vault. Read-only analysis — scans for [[links]] and verifies target files exist. No writes, no dependencies.
+allowed-tools: Grep, Glob, Read
+user-invocable: true
+---
+
+# Check Links Skill
+
+Finds broken `[[wiki-links]]` across your vault by extracting link targets and verifying that each target file exists. Read-only — never modifies files.
+
+## Usage
+
+```
+/check-links
+```
+
+Or ask:
+- "Check for broken links in my vault"
+- "Find dead wiki-links"
+- "Are there any broken links?"
+
+## How to Execute
+
+### Step 1: Extract all wiki-links
+
+Use **Grep** to find all `[[...]]` patterns in markdown files:
+
+```
+Grep:
+  pattern: "\\[\\[([^\\]|]+)"
+  glob: "*.md"
+  output_mode: content
+  -n: true
+```
+
+This captures the link target (before any `|` alias). Exclude `.claude/` and `.obsidian/` directories from results.
+
+### Step 2: Build unique target list
+
+From the grep results, extract the unique link targets. For each match like `[[My Note]]` or `[[My Note|display text]]`, the target is `My Note`.
+
+Strip:
+- Heading anchors: `[[Note#heading]]` → target is `Note`
+- Block references: `[[Note^block-id]]` → target is `Note`
+- Aliases: `[[Note|alias]]` → target is `Note`
+
+### Step 3: Verify each target exists
+
+For each unique target, use **Glob** to check if a matching file exists:
+
+```
+Glob:
+  pattern: "**/<target>.md"
+```
+
+A link is **broken** if no file matches. A link is **valid** if at least one file matches.
+
+### Step 4: Report results
+
+Group broken links by source file:
+
+```markdown
+## Broken Links Report
+
+### Daily Notes/2024-01-15.md
+- [[Projet Alpha]] — no matching file found
+- [[Old Goal]] — no matching file found
+
+### Projects/Project Beta.md
+- [[Meeting Notes Jan]] — no matching file found
+
+---
+
+**Summary:** 3 broken links across 2 files (out of 45 total links checked)
+```
+
+### Step 5: Suggest fixes
+
+For each broken link, try to find a close match:
+
+1. Use **Glob** with a partial pattern: `**/*<partial-target>*.md`
+2. If a similar filename exists, suggest it:
+   ```
+   - [[Projet Alpha]] — Did you mean [[Project Alpha]]?
+   ```
+3. If no close match, just report "no matching file found"
+
+## Edge Cases
+
+- **Embedded images** (`![[image.png]]`) — skip these, they reference attachments
+- **External links** (`[text](https://...)`) — skip these, they are not wiki-links
+- **Template placeholders** (`[[{{date}}]]`) — skip anything with `{{` in the target
+- **Empty links** (`[[]]`) — report as malformed, not broken
+
+## No Broken Links
+
+If all links are valid:
+
+```
+✅ All wiki-links verified — no broken links found across X files (Y links checked)
+```
+
+## Tips
+
+- Run `/check-links` periodically to catch link rot
+- After renaming files, run this to find links that need updating
+- Combine with `/search` to find notes that reference deleted content