fix(rewrite): handle tail/head -n<N> joined flag form

[1llum1n4t1s]

Summary

• Fix tail -n20 file (no space between -n and number) not being rewritten to rtk read file --tail-lines 20
• Add missing head -n 20, head -n20, and head --lines 20 rewrite patterns (only head -20 and head --lines=20 were supported)
• Add 4 new tests covering all new patterns

Root Cause

The TAIL_N_SPACE regex required a mandatory space between -n and the digit (\s+), so tail -n20 fell through unmatched. For head, the -n and --lines <space> forms were never implemented at all.

Test plan

• cargo test test_rewrite_tail — 7 tests pass
• cargo test test_rewrite_head — 7 tests pass
• cargo fmt && cargo clippy --all-targets && cargo test --all — 1357 tests pass, 0 failures
• End-to-end binary verification of all tail/head flag forms

Closes #1108

🤖 Generated with Claude Code

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All committers have signed the CLA.

[pszymkowiak]

[w] wshm · Automated triage by AI

📊 Automated PR Analysis

🐛 Type	bug-fix
🟢 Risk	low

Summary

Fixes tail and head command rewrite patterns to handle the joined flag form (e.g., tail -n20 without a space) and adds missing head -n and head --lines <space> rewrite variants. The TAIL_N_SPACE regex is updated to use \s* instead of \s+, and three new regexes are added for head patterns. Four new tests cover all added patterns.

Review Checklist

• Tests present
• Breaking change
• Docs updated

Linked issues: #1108

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Analyzed automatically by wshm · This is an automated analysis, not a human review.

[1llum1n4t1s]

Closing this PR as it doesn't look like it'll be merged. Feel free to reopen if there's interest. Thanks! 🙏