fix(pricing): verify and remediate Sonnet 5 pricing after the introductory-rate cutoff

[pitimon]

Problem

The curated pricing override records that five edge pricing tables need manual review when the Sonnet 5 introductory period ends on 2026-08-31. Current tests hard-assert the introductory 2/10 price values across those tables.

This is a deadline-driven verification/remediation task. A calendar date alone must not change pricing: official Anthropic and LiteLLM/source data must be checked at the cutoff first.

Scope

• On or after 2026-09-01 in an explicitly recorded timezone, verify the official Anthropic price and the repository's approved source/LiteLLM path.
• Refresh/re-vendor the seed using the established workflow only after values are confirmed.
• Compare the approved source with all five Deno edge pricing patches and update confirmed values/metadata consistently.
• Replace introductory-only assertions with post-cutover or date-independent regression coverage.

Acceptance criteria

• The evidence record identifies the verified source, date, timezone, and confirmed price.
• All five edge tables have equal confirmed values and metadata.
• The curated source and vendored seed agree.
• Pricing and edge-sync tests pass.
• Any normally required edge version/deploy validation is completed before release.

Out of scope

• Automatic price changes based only on the calendar.
• Historical reporting repricing.
• Changing the general LiteLLM/source precedence model.

[pitimon]

Scope shrank after PR #76 (fdf5b59). The "five Deno edge pricing patches" half of this issue is now moot — dashboard/edge-patches/ was deleted, so there are no edge pricing tables left to reconcile.

Remaining scope (still valid): the src-side note in src/lib/pricing/curated-overrides.json:6 —

"sonnet5_intro_price_expiry": "2026-08-31 — Sonnet 5 intro price 2/10 reverts to 3/15 sticker. The src pricing path auto-tracks LiteLLM (no edit needed); re-vendor the seed after the cutover. See issue #16."

On/after 2026-09-01: verify the official Anthropic + LiteLLM price first, then re-vendor seed-snapshot.json via the established workflow. Drop the edge-patch reconciliation and edge-only assertions from the acceptance criteria.