feat(skill): enhance agent skill with save rules, annotation conventions, and pipeline integration

[thoth-bot-ai]

What

Enhances the bundled agent skill (skills/linkledger-cli-agent/SKILL.md) to make it more useful for sub-agents and multi-agent workflows.

Changes

• Setup section: documents wrapper path and DB config so agents don't need to figure out the environment
• When to save: clear rules — save every cited source, every human-shared link, newsletter items; skip throwaway searches
• Annotation conventions: actor naming (agent:<name>), confidence scale guidelines (0.5–1.0 with use-case table), highlight vs lowlight guidance, when to pin
• Content pipeline integration: step-by-step for saving sources during content packet/blog research, linking item IDs to content-board cards

Why

The existing skill covers the how (command syntax) but not the when or why. Sub-agents doing research tasks need opinionated guidance on save discipline, annotation quality, and how LinkLedger fits into a broader content pipeline.

Closes #13 partially (documents the wrapper workaround in the setup section).

[gdiab]

Review findings from my pass:

1. Setup guidance is too environment-specific. skills/linkledger-cli-agent/SKILL.md currently hardcodes /opt/homebrew/bin/linkledger and says it can be called from anywhere. That won’t hold for non-Homebrew/non-macOS setups. Recommend making this conditional and keeping repo-local invocation as default fallback.

2. No env var needed conflicts with repo behavior/docs. The code defaults DB path from current working directory (src/db/database.ts) and docs explicitly support LINKLEDGER_DB_PATH override (README.md). Current wording could send agents to the wrong DB unless wrapper assumptions are true.

Everything else in the PR (when-to-save, annotation conventions, pipeline integration) is a solid improvement.

[thoth-bot-ai]

Good catches — both fixed in 2504a1e:

1. Removed hardcoded /opt/homebrew path. Setup now documents two modes: wrapper-based (if installed) and repo-local invocation as the default fallback.

2. Clarified DB path behavior. Explicitly documents the cwd default, when to set LINKLEDGER_DB_PATH, and the risk of writing to unintended locations without it.

[gdiab]

Re-review complete. The previously reported issues are resolved:

• Setup guidance is now portable (wrapper is conditional, repo-local fallback documented).
• DB path behavior is now aligned with project defaults and LINKLEDGER_DB_PATH override guidance.

No additional blocking findings from this pass.