Fix standard query lockfile detection

[Pybsama]

Summary

• detect existing standard-query pack lockfiles from the real filesystem instead of codeql pack packlist output
• support both qlpack.lock.yml and codeql-pack.lock.yml
• preserve the existing temporary dependency-install and cleanup flow when no lockfile exists

Tests

• npm run test:vscode-integration:no-workspace -- --runTestsByPath test/vscode-tests/no-workspace/local-queries/standard-queries.test.ts
• npm run test:vscode-integration:no-workspace
• npm run build
• npm run lint
• npm run check-types
• npm run lint:markdown

Fixes #4471

[wowjoss334-max]

Fingerprint

[Pybsama]

Revalidated the current GitHub merge tree (f644a136dda8bbb6c246aae479cc289d54cdf3fb) against current main (29fa3448cae0d7ce400a30e851deef923e08e5cc) with the repository-pinned Node 22.21.1 and npm 10.9.4.

• TDD regression proof: reverting only the production fix gives 2 failed / 3 passed; restoring it gives 5 / 5 passing for both qlpack.lock.yml and codeql-pack.lock.yml.
• Focused regression stability: 50 / 50 repetitions passed.
• Full no-workspace integration suite: 51 / 51 suites passed; 366 passed, 3 skipped.
• Unit tests: 65 / 65 suites and 630 / 630 tests passed.
• View tests: 39 / 39 suites passed; 364 passed, 2 skipped.
• npm run build packaged the VSIX successfully.
• TypeScript checks passed in all 7 projects; ESLint, Markdown lint (19 files), scenario lint, dead-code check, changed-file Prettier check, and generated-file consistency all passed.
• Semgrep: 89 TypeScript/Node/security rules over the changed source and test files, 0 findings.
• Production dependency audit: 0 vulnerabilities. The PR does not change dependency manifests or lockfiles.

The worktree remained byte-clean against the GitHub merge tree after generation and validation.