Feature / WIP: TSV sample loading

[lkwhite]

Implements foundation for bulk sample loading via TSV manifest files. This is Phase 1 of a multi-phase implementation.

New Features:

• TSV parser with full error/warning reporting
• Multi-strategy path resolution (absolute, TSV-relative, workspace-relative)
• Sample validation with file existence checks
• Import command UI with preview and confirmation
• Smart loading strategy (eager for small batches, lazy for large)

Files Added:

• src/services/tsv-parser.ts - Parse TSV with validation
• src/services/tsv-path-resolver.ts - Resolve file paths
• src/services/tsv-validator.ts - Validate samples before import
• src/commands/tsv-commands.ts - Import command implementation
• src/services/tests/tsv-parser.test.ts - 28 test cases
• docs/TSV_IMPORT_PROGRESS.md - Implementation progress tracking

Files Modified:

• package.json - Added importSamplesFromTSV command
• src/extension.ts - Registered TSV command

Status:

• ✅ Phase 1 Complete: Parsing & validation
• ⚠️ Phase 2 Partial: UI implemented, kernel loading stubbed
• ⬜ Phase 3 Pending: Actual kernel integration
• ⬜ Phase 4 Pending: UI integration (samples panel grouping, session persistence)

Next Steps:

• Implement actual kernel loading in loadSamplesFromTSV()
• Add lazy loading trigger in plot commands
• Add tests for path resolver and validator
• Integrate with Samples panel UI

Related: Addresses future TSV import feature outlined in docs/TSV_IMPORT_FUTURE_DESIGN.md