fix: preserve canonical executable on cache hits

[Karthik Nadig (karthiknadig)]

Summary

• preserve the canonical executable path on cache hits
• keep caller-facing aliases valid in the current working context
• invalidate stale in-memory entries when tracked executables disappear
• add regressions covering relative/absolute aliases and stale alias validation

Fixes #448
Related: microsoft/vscode-python-environments#1703

Validation

• cargo test -p pet-python-utils --lib
• cargo test --workspace
• cargo fmt --all
• cargo clippy --all -- -D warnings

[github-actions]

Performance Report (Linux)

Result: ✅ Within regression budgets

Metric	PR	Baseline	Delta	Change	Blocking budget	Status
Server startup P50	1ms	1ms	+0ms	+0.0%	>5ms and >100%	➖
Server startup P95	1ms	1ms	+0ms	+0.0%	>50ms and >200%	➖
Full refresh P50	70ms	56ms	+14ms	+25.0%	>25ms and >30%	🔺
Full refresh P95	73ms	60ms	+13ms	+21.7%	>50ms and >50%	🔺
Time to first environment P50	14ms	14ms	+0ms	+0.0%	>20ms and >100%	➖
Time to first environment P95	17ms	21ms	-4ms	-19.0%	>25ms and >100%	✅
Cold refresh P50	172ms	150ms	+22ms	+14.7%	>100ms and >50%	🔺

Workload	PR	Baseline
Environments	5	5
Managers	1	1

A regression must exceed both the documented absolute and relative budget. Environment and manager inventories must match exactly.

[github-actions]

Test Coverage Report (Linux)

Result: ✅ Within regression budget

Metric	PR	Baseline	Delta
Lines	80.815%	80.809%	+0.005pp
Functions	84.806%	84.806%	+0.000pp

Allowed numerical tolerance: 0.01 percentage points.

[github-actions]

Performance Report (macOS)

Result: ✅ Within regression budgets

Metric	PR	Baseline	Delta	Change	Blocking budget	Status
Server startup P50	98ms	105ms	-7ms	-6.7%	>100ms and >50%	✅
Server startup P95	762ms	746ms	+16ms	+2.1%	>750ms and >100%	🔺
Full refresh P50	164ms	194ms	-30ms	-15.5%	>100ms and >50%	✅
Full refresh P95	196ms	211ms	-15ms	-7.1%	>300ms and >100%	✅
Time to first environment P50	113ms	126ms	-13ms	-10.3%	>150ms and >50%	✅
Time to first environment P95	150ms	171ms	-21ms	-12.3%	>250ms and >100%	✅
Cold refresh P50	434ms	383ms	+51ms	+13.3%	>250ms and >50%	🔺

Workload	PR	Baseline
Environments	10	10
Managers	1	1

A regression must exceed both the documented absolute and relative budget. Environment and manager inventories must match exactly.

[github-actions]

Performance Report (Windows)

Result: ❌ Regression detected

Metric	PR	Baseline	Delta	Change	Blocking budget	Status
Server startup P50	8ms	8ms	+0ms	+0.0%	>10ms and >50%	➖
Server startup P95	11ms	12ms	-1ms	-8.3%	>50ms and >100%	✅
Full refresh P50	133ms	151ms	-18ms	-11.9%	>150ms and >50%	✅
Full refresh P95	141ms	159ms	-18ms	-11.3%	>250ms and >100%	✅
Time to first environment P50	18ms	20ms	-2ms	-10.0%	>25ms and >50%	✅
Time to first environment P95	29ms	29ms	+0ms	+0.0%	>100ms and >100%	➖
Cold refresh P50	134ms	153ms	-19ms	-12.4%	>150ms and >50%	✅

Workload	PR	Baseline
Environments	8	10
Managers	1	2

Blocking findings

• Environment inventory changed: current=8, baseline=10
• Manager inventory changed: current=1, baseline=2

A regression must exceed both the documented absolute and relative budget. Environment and manager inventories must match exactly.

[github-actions]

Test Coverage Report (Windows)

Result: ✅ Within regression budget

Metric	PR	Baseline	Delta
Lines	78.229%	78.207%	+0.022pp
Functions	81.573%	81.533%	+0.041pp

Allowed numerical tolerance: 0.01 percentage points.