Consolidate gh-cli and glab-cli into daf-git skill

[itdove]

Background

Investigation found two large reference skills for CLI tools:

Skill	Lines	Content
gh-cli	635	GitHub CLI reference (PRs, issues, API, releases, auth)
glab-cli	611	GitLab CLI reference (MRs, issues, API, pipelines, auth)
Total	1,246

These are never needed simultaneously — a project is either GitHub or GitLab. And daf-git (305 lines) already covers the daf-specific issue operations.

Claude also already has good baseline knowledge of gh and glab commands from training data. The skills mainly add daf-specific patterns (PR templates, fork detection, auth troubleshooting).

Proposal

Merge the daf-relevant parts of gh-cli and glab-cli into daf-git, organized by platform:

## GitHub Operations
### Authentication
### PR Creation (daf complete pattern)
### Fetching files from private repos

## GitLab Operations  
### Authentication
### MR Creation (daf complete pattern)
### Syntax differences from gh

Remove the generic CLI reference content (release management, workflow runs, repo settings) that Claude already knows.

Estimated merged daf-git size: ~400-500 lines (down from 1,551 combined).

Files to Modify

• devflow/cli_skills/daf-git/SKILL.md — add platform-specific sections from gh-cli and glab-cli
• Remove devflow/cli_skills/gh-cli/ directory
• Remove devflow/cli_skills/glab-cli/ directory
• Update cross-references in other skills

Impact

Reduces GitHub/GitLab skill context from 1,551 lines to ~400-500 lines. Combined with #390 (conditional loading), only the relevant platform section loads per session.

• daf-relevant gh-cli content merged into daf-git
• daf-relevant glab-cli content merged into daf-git
• gh-cli and glab-cli directories removed
• Merged daf-git skill is under 500 lines
• Key daf patterns preserved (PR/MR creation, auth, fork detection)
• Cross-references updated
• All tests pass

[itdove]

Dependencies

Blocked by: #388 (remove git-cli first — avoids merging content that will be deleted)
Blocks: #390 (conditional loading is easier with fewer consolidated skills)

Execution phase: Phase 2B (after #388, can run in parallel with #391)

Related: Part of skills optimization (#388-#392)