feat(tooling): upgrade ESLint 9 → 10 with flat config migration (#171)

* chore(deps): upgrade eslint 9->10, replace import plugin with import-x

- eslint ^9 -> ^10 (10.4.0)
- @cdklabs/eslint-plugin ^1 -> ^2 (flat config support)
- eslint-plugin-import removed (no ESLint 10 support)
- eslint-plugin-import-x ^4 added (drop-in replacement)
- eslint-import-resolver-typescript removed (import-x has built-in TS resolution)
- Root resolution for eslint-plugin-import/minimatch removed

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(eslint): migrate cdk/ to ESLint 10 flat config

Convert .eslintrc.json to eslint.config.mjs (ESM flat config format).
Replace import/ rule prefix with import-x/. Remove --ext flag and
ESLINT_USE_FLAT_CONFIG env var from the eslint script.

All existing rules preserved with equivalent flat config syntax.
Four @cdklabs rules (no-core-construct, invalid-cfn-imports,
no-literal-partition, no-invalid-path) are temporarily disabled
because they use context.getFilename() which was removed in ESLint 10.
Stale eslint-disable comments for disabled/absent rules removed by
auto-fix.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* feat(eslint): migrate cli/ to ESLint 10 flat config

Convert .eslintrc.json to eslint.config.mjs. Replace import/ rule
prefix with import-x/. Remove --ext flag and ESLINT_USE_FLAT_CONFIG.
All existing rules preserved including no-console override for src/.
Removed stale no-constant-condition disable comments (rule deprecated
in ESLint 10).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(eslint): restore eslint-import-resolver-typescript for import-x

The resolver is required by eslint-plugin-import-x for TypeScript path
resolution. Was incorrectly removed in the package upgrade commit.
Also disable license-header rule for shebang bin files (workaround).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix(eslint): remove stale suppressions from merged attachments code

ESLint --fix removes no-op suppression comments for rules not enabled
in our config. These were introduced by the attachments PR (#176) merge
and are cleaned up by the new ESLint 10 flat config.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: bgagent <345885+scottschreckengaust@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: Alain Krok <alkrok@amazon.com>

Author: 3 people