[fp-enhancer] Improve pkg/cli - functional/immutability enhancements (round 1)

[github-actions]

This PR applies moderate, tasteful functional/immutability techniques to the pkg/cli package to improve code clarity and maintainability.

Round-Robin Progress: First package processed. Next run will process: pkg/console

Summary of Changes

1. Declarative Slice Initialization (tool_graph.go)

Replaced a manual 4-line loop + sort.Strings with a single declarative expression:

// Before
var tools []string
for tool := range g.Tools {
    tools = append(tools, tool)
}
sort.Strings(tools)

// After
tools := slices.Sorted(maps.Keys(g.Tools))

This pattern is already used elsewhere in pkg/cli (e.g., run_workflow_validation.go), making this consistent with existing codebase style.

2. Pre-allocated Slice (tool_graph.go)

Pre-allocate transitions slice with known capacity to avoid incremental growth:

// Before
var transitions []ToolTransition

// After
transitions := make([]ToolTransition, 0, len(g.Transitions))

3. Type-safe Sort (tool_graph.go)

Replaced sort.Slice (index-based, untyped) with slices.SortFunc (typed comparison):

// Before
sort.Slice(transitions, func(i, j int) bool {
    if transitions[i].Count != transitions[j].Count {
        return transitions[i].Count > transitions[j].Count
    }
    ...
})

// After
slices.SortFunc(transitions, func(a, b ToolTransition) int {
    if a.Count != b.Count {
        return b.Count - a.Count // descending by count
    }
    ...
})

Side effect: the "sort" import is replaced with "maps" and "slices" (standard library packages).

4. Pre-allocated Slice (actionlint.go)

Pre-allocate relPaths with known capacity from len(lockFiles):

// Before
var relPaths []string

// After
relPaths := make([]string, 0, len(lockFiles))

Testing

• ✅ TestToolGraph, TestToolGraphMultipleSequences, TestToolGraphEmptySequences all pass
• ✅ All actionlint tests pass
• ✅ go build ./pkg/cli/ succeeds
• ✅ make fmt passes
• ✅ No behavioral changes — functionality is identical

Benefits

• Clarity: Declarative slices.Sorted(maps.Keys(...)) communicates intent in one line
• Consistency: Matches patterns already used in run_workflow_validation.go
• Safety: slices.SortFunc is type-safe vs index-based sort.Slice
• Performance: Pre-allocation avoids slice growth reallocations

---

Automated by Functional Pragmatist — processing pkg/cli (round 1 of N). Next: pkg/console

Generated by Functional Pragmatist · ◷

• expires on Apr 1, 2026, 9:34 AM UTC

[pelikhan]

/q update prompt to avoid calling make with a length, it triggers codeql violations.

[github-actions]

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[github-actions]

Issue created: #23684

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