Price current Claude 5 and Gemini 3.6 models

[mostlydev]

Summary

• price Claude Fable 5, Opus 5, and Sonnet 5 for direct Anthropic and OpenRouter routes
• price Gemini 3.6 Flash for direct Google and OpenRouter routes
• correct Claude Haiku 4.5 from the retired Haiku 3.5 rate to its current 1/5 rate
• keep every older pricing row for compatibility

Sonnet 5 uses the published standard 3/15 rate as a conservative static ceiling. Anthropic and OpenRouter currently apply promotional 2/10 pricing through August 31, 2026; using the standard ceiling prevents budget enforcement from silently undercounting after that date.

Official pricing sources:

• https://platform.claude.com/docs/en/about-claude/pricing
• https://platform.claude.com/docs/en/about-claude/models/overview
• https://ai.google.dev/gemini-api/docs/pricing
• https://ai.google.dev/gemini-api/docs/models/gemini-3.6-flash

Verification

• go test ./...
• go vet ./...

Closes #40

[mostlydev]

Adversarial review (claude): ACCEPT at f6057c0.

Verified: full test + vet green at head in an isolated worktree; PR is one commit based directly on master head 11aa5a3; every pre-existing row retained; Sonnet 5 conservative post-promotion ceiling is the right budget-enforcement call (undercounting after 2026-08-31 would be silent).

Checked lookup semantics against the new rows: exact-then-longest-prefix means openrouter/anthropic/claude-sonnet-4-6 (used by downstream examples) resolves via the claude-sonnet-4 prefix at the same 3/15 rate — no gap.

Non-blocking note: the new OpenRouter haiku row is keyed anthropic/claude-haiku-4.5 (dot, live catalog slug) while direct-Anthropic uses claude-haiku-4-5 (dash). The dash form under the openrouter provider gets no row and no prefix match — zero-cost telemetry. Nothing in-tree does this; if it shows up in operator reports, add a dash alias rather than renaming.