Rust parity · slice 4/11 — input parsing (serde-typed Session) #82

Part of #27 · parity v1, slice 4/11 · implemented in #47 (base rust-parity-v1).

Scope

• input.rs: JSON to a typed Session with every field bash reads in its single jq pass (model, context window, transcript path, session id, rate limits, current usage).
• Derivations: tokens_used, subagent transcript to parent .jsonl, Antigravity client detection and /antigravity/ to /antigravity-cli/ path correction, is_gemini.

Bash oracle

parse_and_prepare_paths in tokenline.sh.

Done when

• cargo fmt --check, cargo clippy --all-targets -- -D warnings and cargo test are green
• Each derivation matches bash for the same payload, and missing fields default like // "" / // 0
• feat: input parsing — serde-typed Session (parity v1 · slice 4/11) #47 is merged into rust-parity-v1 with a merge commit, not squash or rebase, so the stacked slices above stay valid

Notes

• Known parity gap, fixed in slice 12 (Rust parity · slice 12 — absorb main fixes: Fable 5.1 (0.025x, #74) + Opus 5.5 (0.05x, #102) cache-read + Gemini match parity #76), not here: bash detects Gemini with [[ $model =~ [Gg]emini ]], while input.rs uses to_lowercase().contains("gemini"), so a name like GEMINI classifies differently. Fixing it in this PR would force a re-stack of slices 5 to 11.
• model.id is added in slice 12 (Rust parity · slice 12 — absorb main fixes: Fable 5.1 (0.025x, #74) + Opus 5.5 (0.05x, #102) cache-read + Gemini match parity #76) for the Fable 5.1 / Mythos 5.1 cache-read multiplier (Cache-read multiplier is wrong on Claude Fable 5.1 / Mythos 5.1 (0.025x, not 0.1x) #74).

#47 targets rust-parity-v1, not the default branch, so closing keywords do not fire. Close this issue by hand when #47 merges, and tick the slice in the #27 checklist.