chore(#2177): add lint-docs-links check; fix all escaping docs/ links

[rh-hemartin]

Summary

• Adds hack/lint-docs-links, a pre-commit hook that rejects relative links in docs/ that resolve outside the docs/ tree
• Wires the hook into .pre-commit-config.yaml (runs on all docs/**/*.md files)
• Fixes all 53 pre-existing violations by converting escaping relative links to absolute github.com/fullsend-ai/fullsend/blob/main/… URLs

Links that escape docs/ are broken on fullsend.sh, which only serves the docs/ tree.

Closes #2177.

Test plan

• make lint passes (lint-docs-links runs as part of pre-commit)
• ./hack/lint-docs-links $(git ls-files docs/ | grep '\.md$') exits 0
• Introducing a new escaping link in docs/ causes the hook to fail

🤖 Generated with Claude Code

[github-actions]

Site preview

Preview: https://9079eac1-site.fullsend-ai.workers.dev

Commit: 1c8577f9019104aefeaa2921375bcb27f5d85cd4

[fullsend-ai-review]

🤖 Finished Review · ✅ Success · Started 3:13 PM UTC · Completed 3:21 PM UTC
Commit: 1c8577f · View workflow run →

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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[fullsend-ai-review]

Review

Findings

Medium

• [protected-path] .pre-commit-config.yaml — This PR modifies .pre-commit-config.yaml, which is a protected path requiring human approval. The change is well-justified (adds a new lint-docs-links hook per issue lint: reject docs/ links that resolve outside docs/ #2177), but human review is always required for protected-path changes regardless of context.

Low

• [logic-error] hack/lint-docs-links:31 — The prefix check [[ "$resolved" != "$docs_dir"* ]] would also match paths under a hypothetical sibling directory starting with docs (e.g., docs-legacy/). Currently no such directory exists in the repo, making this theoretical.
  Remediation: Change to if [[ "$resolved" != "$docs_dir/"* ]] to require the trailing slash.

• [edge-case] hack/lint-docs-links:33 — The link-extraction regex (?<=\])\(\K[^)]+ captures Markdown title attributes (e.g., [text](path "title")). The title text is not stripped before realpath -m, which would cause false positives on links with title attributes. Currently no docs files use this syntax, so the issue is latent.
  Remediation: Strip optional title after extraction: path="${path%% \"*}".

Info

• [intent-alignment] PR correctly traces to authorized work (issue lint: reject docs/ links that resolve outside docs/ #2177) and implements exactly the requested scope: lint hook + fix all 53 violations.

[ralphbean]

LGTM. Link conversions all check out — correct paths, correct blob/tree usage, intra-docs links left alone.