fix: resolve symlinked /bin/python3 as LinuxGlobal (Fixes #405)

[karthiknadig]

When /bin is a symlink to /usr/bin (common on modern Linux distros), find_cached() canonicalizes /bin → /usr/bin and only caches entries under /usr/bin. A subsequent try_from call with /bin/python3 fails the direct cache lookup and returns None, causing the environment to be reported as Unknown.

Fix: In try_from, after a cache miss, canonicalize the executable path and retry the lookup. When found via the canonical path, add the original path as a symlink and update both cache entries for consistency.

• Canonicalize executable once, use for both path guard and cache fallback
• Path guard accepts executables whose canonical path resolves to a known bin dir
• Cache fallback adds the original path as a symlink for complete metadata
• Both canonical and original cache entries updated to keep symlink lists consistent

Fixes #405

[github-actions]

Test Coverage Report (Linux)

Metric	Value
Current Coverage	73.4%
Base Branch Coverage	73.5%
Delta	-.1% ❌

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Coverage decreased. Please add tests for new code.

[github-actions]

Performance Report (Linux) ✅

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	1ms	1ms	1ms	0ms	0%
Full Refresh	71ms	270ms	79ms	-8ms	-10.0%

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]

Performance Report (macOS)

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta
Server Startup	57ms	492ms	87ms	-30ms
Full Refresh	128ms	26124ms	163ms	-35ms

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]

Performance Report (Windows) ➖

Metric	PR (P50)	PR (P95)	Baseline (P50)	Delta	Change
Server Startup	9ms	11ms	9ms	0ms	0%
Full Refresh	150ms	1531ms	146ms	4ms	2.7%

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	69.61%
Base Branch Coverage	69.73%
Delta	-0.12% ❌

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Coverage decreased. Please add tests for new code.