Fix staticcheck SA9003: Replace empty if blocks with explicit error discard

[Copilot]

The staticcheck linter (SA9003) flagged three empty if blocks in internal/logger/markdown_logger.go where Sync() errors were being silently ignored.

Changes

• Replaced empty if blocks with explicit _ = err pattern (idiomatic Go for intentional error discard)
• Affected locations: lines 103, 108, and 186 in markdown_logger.go

Before:

if err := ml.logFile.Sync(); err != nil {
    // Ignore sync errors
}

After:

_ = ml.logFile.Sync() // Ignore sync errors

Behavior is unchanged - errors are still intentionally ignored in all three locations.

Original prompt

Reference: https://github.com/githubnext/gh-aw-mcpg/actions/runs/20896724928/job/60036773633#step:6:1

Fix linter issues

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