refactor(runtime-host): remove redundant TraceTotals from Session traces

[Sun-GLiang]

Summary

• Remove TraceTotals, its helpers, and the redundant aggregate fields from Core, Runtime, Runtime Host, preload, and Desktop trace shapes.
• Derive each Inspector turn's optional cost from already-aggregated model_call step prices, preserving unpriced, mixed, retry, and explicit-zero semantics without rescanning attempts.
• Reject legacy page-level and nested-turn totals at the Runtime Host boundary and advance the compatibility epoch from 35 to 36.

Fixes #3389

Verification

• npm test — all workspace tests passed
• npm run build:test
• npm --workspace @maka/desktop run typecheck
• npm run lint
• npm run format:check
• node --test --test-concurrency=1 scripts/protocol-epoch-check.test.mjs — 8 passed
• node scripts/protocol-epoch-check.mjs --base apache/main --head HEAD — protocol changed and epoch moved 35 → 36
• git diff --check apache/main...HEAD

Review focus

SESSION_TRACE_SCHEMA_VERSION intentionally remains 1 because this projection is not persisted. Cross-process compatibility is enforced by Runtime Host compatibility epoch 36.

AI use

Select exactly one:

• No generative tool made a substantive contribution
• Generative tooling made a substantive contribution

Tool(s) and scope: Codex — issue analysis, implementation, tests, verification, and draft PR preparation.

Checklist

• Tests cover the change and fail without it
• Lint, format, typecheck and the affected suites pass locally

Does this PR entail a change in behavior?

• Yes — described under Summary above
• No