feat: add AWS Bedrock in-region Claude pricing - #95

Summary

Adds selectable AWS Bedrock in-region pricing for Claude Code usage and keeps cached aggregates consistent when pricing changes.

Added Bedrock model rates

• Claude Opus 4.5, 4.6, 4.7, and 4.8
• Claude Sonnet 4.5 and 4.6
• Existing Claude Opus 5, Sonnet 5, and Haiku 4.5 Bedrock rates retained
• Separate 5-minute and 1-hour cache-write rates
• Regional Bedrock model IDs such as us.anthropic.* are recognized
• Direct Anthropic pricing remains the default; AWS Bedrock pricing is opt-in through the Claude settings panel

Model-ID handling

• Normalizes dated Claude model IDs such as claude-sonnet-4-5-20250929
• Handles Bedrock inference-profile prefixes such as us.anthropic.*
• Treats dotted and underscored model labels consistently with native hyphenated Claude IDs
• Prevents Sonnet 4.5 Bedrock usage from falling back to direct Anthropic rates

Cache correctness

Changing the pricing backend now invalidates the incremental Claude usage index so totalCost, model totals, and cost breakdowns are recalculated immediately. The same invalidation is applied after refreshing token pricing.

UI changes

• Added the Claude pricing backend dropdown to the Claude Settings panel
• Provides Anthropic direct API and AWS Bedrock (in-region) options
• Keeps the Bedrock pricing control scoped to Claude and hidden from Codex settings
• Selecting the Bedrock option sends the expected updateSetting message to the extension host

Tests and validation

• npm run test:release
• Node suite: 617 passed, 1 skipped
• Playwright UI suite: 65 passed
• Added focused pricing coverage for the requested Opus and Sonnet model families
• Added UI coverage for dropdown visibility, provider scoping, option labels, default selection, and Bedrock selection messaging
• Verified the packaged VSIX and local installation separately as version 2.3.1

The Bedrock mode remains opt-in; direct Anthropic pricing remains the default.