feat: add glab (GitLab CLI) proxy support

[Smasherr]

Summary

• Add token-optimized filtering for GitLab CLI (glab) commands, following the established gh_cmd.rs pattern
• Filter mr list/view, issue list/view, ci list/trace, release view with 40-97% token savings
• All other glab subcommands (api, pipeline, etc.) pass through with usage tracking
• Include discover rules for automatic hook rewrite (glab -> rtk glab)

Closes #851

Coverage

Command	Strategy	Savings
glab mr list	JSON -> compact text with state/draft icons	~97%
glab mr view	JSON -> essential fields + filtered description	~93%
glab issue list	JSON -> compact text with state icons	~80%
glab issue view	JSON -> essential fields + filtered description	~75%
glab ci list	JSON -> status icons + ref + source	~90%
glab ci trace	Strip ANSI, section markers, runner boilerplate	~40-60%
glab release view	Strip SOURCES block + markdown noise	~63%
glab release list	Passthrough (already compact text)	tracked
glab api, glab *	Passthrough	tracked

Test plan

• cargo fmt --all && cargo clippy --all-targets && cargo test (1132 passed, 0 failed)
• Manual testing: rtk glab mr list, rtk glab mr view, rtk glab ci list, rtk glab ci trace, rtk glab release view output inspected
• rtk gain --history confirms savings: mr list 97%, mr view 93%, ci list 90%, release view 63%
• rtk rewrite "glab mr list" outputs rtk glab mr list (hook integration works)

[CLAassistant]

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✅ Smasherr
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[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling