feat: add brace expansion support for glob patterns

[karthiknadig]

Adds {a,b} brace expansion support to glob pattern handling, enabling patterns like ./**/{bin,Scripts}/python{,.exe} to work as search paths.

Changes

• Brace expansion in pet-fs/src/glob.rs: expands {a,b} groups before passing patterns to the glob crate (which doesn't support braces natively)
• Safety cap: expansion limited to 1024 patterns to prevent exponential blowup
• Progress logging: trace-level logs during glob expansion showing pattern, match count, and elapsed time
• Robust detection: is_glob_pattern() correctly identifies brace patterns (requires matched {...} pair with comma, scans all groups)
• JSONRPC docs: documented brace expansion syntax and example in searchPaths
• Comprehensive tests: 27 new tests covering edge cases, cap behavior, filesystem integration, and performance

Fixes #366

[github-actions]

Performance Report (Linux) ➖

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	1ms	1ms	1ms	0ms	0%
Full Refresh	100ms	317ms	96ms	4ms	0%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

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Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)

[github-actions]

Test Coverage Report (Linux)

Metric	Value
Current Coverage	64.0%
Base Branch Coverage	62.7%
Delta	1.3% ✅

---

Coverage increased! Great work!

[github-actions]

Performance Report (macOS)

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta
Server Startup	50ms	447ms	66ms	-16ms
Full Refresh	92ms	25738ms	114ms	-22ms

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

---

Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)

[github-actions]

Test Coverage Report (Windows)

Metric	Value
Current Coverage	60.21%
Base Branch Coverage	58.89%
Delta	1.32% ✅

---

Coverage increased! Great work!

[github-actions]

Performance Report (Windows) ➖

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	10ms	13ms	9ms	1ms	11.1%
Full Refresh	167ms	3458ms	165ms	2ms	1.2%

Results based on 10 iterations. P50 = median, P95 = 95th percentile.

---

Legend

• 🚀 Significant speedup (>100ms faster)
• ✅ Faster than baseline
• ➖ No significant change
• 🔺 Slower than baseline (>100ms)
• ⚠️ Significant slowdown (>500ms)