Fix golangci-lint failures in codemod and miner test files

[Copilot]

Bug Fix

What was the bug?

The lint-go CI job was failing with 7 golangci-lint violations across three files introduced by recent changes.

How did you fix it?

pkg/cli/codemod_checkout_persist_credentials_false.go

• intrange: replaced C-style loop with for i := range stepLines
• wastedassign: moved isUsesInline and withKeyIndentLen declarations into the if blocks where they're first assigned and used, eliminating dead initial values
• perfsprint: replaced fmt.Sprintf("%spersist-credentials: false", withIndent+" ") with withIndent + " persist-credentials: false"; removed unused "fmt" import

pkg/cli/codemod_checkout_persist_credentials_false_fuzz_test.go

• perfsprint: replaced two fmt.Sprintf("...: %s", x) calls with string concatenation; removed unused "fmt" import

pkg/agentdrain/miner_test.go

• testifylint: swapped require.NoError → assert.NoError inside a goroutine — require calls runtime.Goexit() which doesn't behave correctly outside the test goroutine

[Copilot]

Pull request overview

This PR fixes golangci-lint violations that were causing the lint-go CI job to fail, without changing the intended runtime behavior.

Changes:

• Refactors the codemod implementation to remove intrange, wastedassign, and perfsprint lint violations (including dropping an unused fmt import).
• Updates the codemod fuzz test to avoid unnecessary fmt.Sprintf usage and remove the unused fmt import.
• Replaces require.NoError with assert.NoError inside a goroutine in TestConcurrency to avoid runtime.Goexit() behavior from non-test goroutines.

Show a summary per file

File	Description
pkg/cli/codemod_checkout_persist_credentials_false.go	Refactors loop/assignments and simplifies string construction to satisfy golangci-lint.
pkg/cli/codemod_checkout_persist_credentials_false_fuzz_test.go	Removes fmt.Sprintf usage and unused import in fuzz test helper.
pkg/agentdrain/miner_test.go	Avoids require.* assertions inside goroutines by switching to assert.*.

Copilot's findings

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• Files reviewed: 3/3 changed files
• Comments generated: 0