perf: pre-compile command templates in CommandExecutor

[abtreece]

Summary

• Pre-compile check_cmd and reload_cmd templates at construction time instead of parsing on every execution
• Detect invalid command templates early at initialization rather than at runtime
• Add benchmarks comparing pre-compiled vs parse-per-call approaches

Benchmark Results

Approach	Time	Memory	Allocations
Pre-compiled (new)	~305 ns/op	320 B/op	8
Parse-per-call (old)	~3010 ns/op	6157 B/op	64

Improvement: 10x faster, 19x less memory, 8x fewer allocations

Test plan

• All existing command executor tests pass
• Invalid template tests updated to expect errors at construction time
• Full test suite passes (go test ./...)
• Build succeeds (make build)
• Benchmarks added to verify performance improvement

Fixes #444

[Copilot]

Pull request overview

This PR improves performance of command template handling by pre-compiling check and reload command templates at initialization rather than parsing them on every execution. Invalid templates are now detected early during construction, improving error feedback.

Changes:

• Pre-compile command templates in commandExecutor constructor
• Update newCommandExecutor to return error for invalid templates
• Refactor tests to handle new constructor signature and verify early error detection

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
pkg/template/command_executor.go	Added pre-compiled template fields and template parsing logic to constructor
pkg/template/command_executor_test.go	Updated tests to handle error-returning constructor and moved template validation tests to construction time
pkg/template/resource.go	Added error handling for newCommandExecutor calls in three locations

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[codecov]

Codecov Report

❌ Patch coverage is 85.18519% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.76%. Comparing base (408f57b) to head (2bd5bf2).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/template/command_executor.go	86.66%	0 Missing and 2 partials ⚠️
pkg/template/resource.go	83.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #456      +/-   ##
==========================================
- Coverage   59.80%   59.76%   -0.05%     
==========================================
  Files          48       48              
  Lines        5230     5244      +14     
==========================================
+ Hits         3128     3134       +6     
- Misses       1897     1904       +7     
- Partials      205      206       +1     

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