Filter migrations to only run numbered files, skip bootstrap helpers

[Copilot]

The runMigrations function was executing all .sql files in migrations/, including bootstrap_existing_db.sql which is intended as a one-time manual operation for existing databases.

Changes

• Added regex filter ^\d{3}_.*\.sql$ to match only numbered migrations (001_init.sql, 002_sample_data.sql, etc.)
• Skip non-numbered files with log message
• Compile pattern once at function start to avoid repeated overhead

Implementation

func runMigrations(db *database.DB) error {
    // Compile regex pattern once for efficiency
    migrationPattern := regexp.MustCompile(`^\d{3}_.*\.sql$`)
    
    // ... existing setup code ...
    
    for _, entry := range entries {
        if entry.IsDir() || !strings.HasSuffix(entry.Name(), ".sql") {
            continue
        }
        
        // Skip non-numbered migration files (e.g., bootstrap scripts)
        if !migrationPattern.MatchString(entry.Name()) {
            log.Printf("Skipping non-numbered migration file: %s", entry.Name())
            continue
        }
        
        // ... execute migration ...
    }
}

Bootstrap scripts like bootstrap_existing_db.sql now stay manual-only as documented.

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[Copilot]

Pull request overview

This PR enhances the database migration system to filter and execute only numbered migration files while skipping helper scripts that are intended for manual execution.

Changes:

• Added regex pattern ^\d{3}_.*\.sql$ to match only numbered migrations (001_init.sql, 002_sample_data.sql, etc.)
• Implemented filtering logic to skip non-numbered migration files with logging
• Compiled regex pattern once at function start for efficiency

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[Copilot]

The new filtering logic that skips non-numbered migration files lacks test coverage. Consider adding tests to verify that:

1. Numbered migration files (e.g., 001_init.sql) are processed correctly
2. Non-numbered files (e.g., bootstrap_existing_db.sql) are skipped with appropriate logging
3. Edge cases like files with partial number patterns are handled correctly

Other functions in the codebase have comprehensive test coverage (see tests/a2a/, internal/models/models_test.go, internal/validator/validator_test.go), suggesting that adding tests for this migration filtering logic would be consistent with project practices.