fix(goctl): restore API summaries in swagger generation

[kevwan]

Description

Fixes #5229

The getFirstUsableString() function was only handling Go-quoted strings, causing all API summaries (from @doc text and handler names) to be lost in swagger output after the refactoring in commit cf21cb2.

Changes

• Fix getFirstUsableString() to handle both quoted and unquoted strings
• Add fallback to use value as-is when unquoting fails
• Add 17 comprehensive unit tests covering all scenarios

Root Cause

The function tried to unquote plain strings like "Check server health status." using strconv.Unquote(), which expects Go-quoted strings like "\"Check server health status.\"". When unquoting failed, it returned an empty string.

Testing

• ✅ All 17 new unit tests pass
• ✅ All existing swagger tests pass
• ✅ Verified swagger generation produces correct summaries
• ✅ No regressions introduced

Before Fix

{
  "paths": {
    "/xz-server/health": {
      "get": {
        "summary": "",  // ❌ Empty!
        "operationId": "healthCheck"
      }
    }
  }
}

After Fix

{
  "paths": {
    "/xz-server/health": {
      "get": {
        "summary": "Check server health status.",  // ✅ Restored!
        "operationId": "healthCheck"
      }
    }
  }
}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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