## Summary
- remove the final whole-blob truncation pass from realtime
startup-context assembly
- enforce fixed per-section budgets, including each section heading
- keep the existing per-section caps and raise the overall realtime
startup-context budget to `5300`, matching the sum of those section
budgets
- add focused tests for the new wrapping and section-budget behavior
## Why
The previous flow truncated each section and then middle-truncated the
final combined startup-context blob again. Small input changes could
shift that combined cut point, which made retained context unstable and
caused nondeterministic tests.
## Impact
Startup context now preserves section boundaries and ordering
deterministically. Each section is still budgeted independently, but the
final assembled blob is no longer truncated again as a single opaque
string. To match that design, the overall startup-context token budget
is updated to the sum of the existing section budgets rather than
lowering the section caps.
## Validation
- `cargo +1.93.0 test -p codex-core realtime_context`
- `cargo +1.93.0 test -p codex-core --test all
suite::realtime_conversation::conversation_start_injects_startup_context_from_thread_history
-- --exact`
- `cargo +1.93.0 test -p codex-core --test all
suite::realtime_conversation::conversation_startup_context_current_thread_selects_many_turns_by_budget
-- --exact`
- `cargo +1.93.0 test -p codex-core --test all
suite::realtime_conversation::conversation_startup_context_falls_back_to_workspace_map
-- --exact`
- `cargo +1.93.0 test -p codex-core --test all
suite::realtime_conversation::conversation_startup_context_is_truncated_and_sent_once_per_start
-- --exact`
bxie-openai
37bf42d5d5