Port upstream 0.70.0: Antigravity Gemini 3.1 Pro pricing aliases (stacked on #706)

[Finesssee]

Summary

Antigravity records Gemini 3.1 Pro under product aliases and effort tiers (gemini-pro-default, gemini-pro-agent, gemini-3.1-pro, gemini-3.1-pro-high, gemini-3.1-pro-low, and suffixed forms such as gemini-3.1-pro-thinking). None of these names is a catalogued model, so this history stayed unpriced. These rows now get list-price estimates from gemini-3.1-pro-preview, the only catalogued Gemini 3.1 Pro row.

• Lookup order is unchanged from upstream: the exact recorded model first (so an explicitly catalogued alias keeps its own price), then the pricing base. The base is an alias's catalogued model, or the base of a -tiered / -low / -thinking routing variant resolved through the same alias table.
• Aliases match case-insensitively (Gemini-Pro-Default).
• The alias table is Antigravity-local (rust/src/providers/antigravity/cost.rs). Shared Claude/models.dev pricing still reports unknown variants as unpriced.
• Recorded model names are never rewritten. LocalCostEstimate::unpriced_models keeps the recorded name. An unpriced alias also adds google/gemini-3.1-pro-preview to the bounded models.dev refresh that Port upstream 0.64.0: Antigravity cost follow-ups - lower bounds, withheld reads, --refresh (stacked on #610) #706 introduced.

Stacked on #706 (port/micro-0.64.0-antigravity-cost-followups) rather than #610, because #706 rewrites the same cost.rs (refresh targets) and the docs/CLI.md Antigravity paragraph. Merge after #706.

Upstream reference

• steipete/CodexBar v0.70.0, PR Price aliased Antigravity and Codex models steipete/CodexBar#4094 (commit 84669209372e4871be073d8a0c62d01cd0cb82c5), Antigravity half only: AntigravityLocalReader.pricingBaseModelID(for:), pricingModelAliases, costUSD (exact model, then base).
• Tests translated from AntigravityLocalReaderTests (v0.70.0): the pricingBaseModelID expectations (gemini-3.8-flash-tiered, gemini-3.1-pro-low, claude-opus-4-6-thinking, gemini-3.8-flash -> none, -low -> none, the five aliases, Gemini-Pro-Default). Also "gemini pro product aliases price from the catalogued preview model": google gemini-3.1-pro-preview at input 1 / output 2 / cache read 0.2 USD per million tokens, expected 111e-6 + 50 * 0.2e-6 + 37 * 2e-6. Also the shared-target guard (claude-fixture-9-thinking targets do not include claude-fixture-9).

Ported / Deferred

Ported:

• The alias table and its resolution order, with case-insensitive matching.
• An alias reached through a routing suffix, which upstream also handles (pricingModelAliases[base.lowercased()] ?? base).
• The docs note (docs/CLI.md, Antigravity cost paragraph).

Windows differences:

• Windows has no per-model Antigravity cost breakdown, so upstream's "breakdown keeps gemini-pro-default" assertion has no direct counterpart. Its intent is kept: pricing resolves without renaming the recorded model, and unpriced rows keep the recorded name.
• The tests price through an injected models.dev snapshot (estimate_cost_usd_with plus ModelsDevPricingSnapshot::from_catalog_json_for_tests), using the same built-in-then-routed resolution as production. They never read the per-user models.dev cache.

Deferred:

• The Codex half of upstream Price aliased Antigravity and Codex models steipete/CodexBar#4094 (Codex model aliases in core/cost_pricing.rs) is a separate v0.70.0 backlog item, "Codex Sol cutoff, Cyber rates and daybreak aliases", owned by another lane.
• The CHANGELOG entry is left to the release/v0.70.0 integration, like the sibling micro PRs in this stack.

Validation

At 77dc904a (in W:\wcb-wt\lane-a, toolchain 1.98.0):

• cargo +1.98.0 fmt --all --check: pass
• cargo +1.98.0 clippy --workspace --all-targets -- -D warnings: pass
• cargo +1.98.0 test -p codexbar --lib antigravity::cost: 10 passed (5 new)
• cargo +1.98.0 test -p codexbar: 2252 passed, 0 failed, 1 ignored
• cargo +1.98.0 test -p codexbar-desktop-tauri: 478 passed, 1 failed. The failure is bootstrap_payload_exposes_every_provider_variant, the known hardcoded-count drift from Isolate bootstrap payload test from real settings #684 that Make the bootstrap catalog test hermetic (#684) #711 fixes. It is unrelated to this change.
• Frontend unchanged.

Affected areas

• rust/src/providers/antigravity/cost.rs: alias table, pricing_base_model, injectable estimate_cost_usd_with, and tests.
• docs/CLI.md: the Antigravity cost paragraph.

UI proof

Not applicable: this is a backend pricing change only, with no UI or locale change. The existing Usage & Spend rendering shows the resulting estimate, which unit tests cover.

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[Finesssee]

Adversarial validation passed at a49d1b5

Scope: Antigravity Gemini 3.1 Pro pricing aliases (#732, upstream 0.70.0 steipete#4094/8466920937, audit row 5a), validated as merged into release/v0.70.0 (merge a49d1b5 = merge of 77dc904 into 8a8f3f5).

Attacks (against the 0.70.0 audit behavior spec, audit-0.70.0.md row 5a):

• Alias coverage: the merged tree maps gemini-pro-default, gemini-pro-agent, gemini-3.1-pro, gemini-3.1-pro-high and gemini-3.1-pro-low (case-insensitive) to gemini-3.1-pro-preview — all five aliases the audit named — with the -tiered/-low/-thinking routing suffixes stripped first so gemini-3.1-pro-high-thinking prices the preview row, matching upstream 8466920.
• Near misses stay unaliased: the catalogued row itself (gemini-3.1-pro-preview) needs no base, gemini-pro (no version) is NOT inferred, gemini-3.1-pro-max and the flash family stay out of the Pro alias table; gemini-3.8-flash-tiered still routes to its own base, so the alias table is genuinely provider-local and not a catch-all.
• Provider-locality preserved: the alias resolution lives in pricing_base_model, which is only consulted by the Antigravity cost path; the shared CostUsagePricing Claude path never sees it — the audit's "shared Claude pricing keeps unknown variants unpriced" rule holds. A claude-fixture-9-thinking test asserts the shared resolver still reports it unpriced rather than silently billing it at the base rate.
• Recorded model names unchanged: the estimate annotates the pricing base but never rewrites the recorded model id, matching the audit's "The recorded model name itself is never rewritten; only the price lookup resolves."
• Fallback ordering: the aliases are checked BEFORE the routing-suffix strip in pricing_base_model, so a plain gemini-3.1-pro-low resolves via the alias without needing the suffix path, matching upstream ordering.

No defects found. READY for the un-draft rule.