apply the compaction effort cap to requests naming no effort

[rikbrown]

Problem

src/providers/codex/translate/request.rs:

if apply_codex_config
    && is_compact
    && let Some(cap) = compact_effort_cap()
    && resolved_effort.as_ref().is_some_and(|e| *e > cap)
{
    resolved_effort = Some(cap);
}

is_some_and means the cap only ever lowers an effort that is already present. A compaction request naming no effort at all skips the cap entirely and runs at the upstream default — which is the effort level the cap exists to avoid.

That is also the case it is most needed for: Claude Code's own /compact request carries no effort of its own, so the fast path never applied to it.

Fix

apply_compact_effort_cap resolves the two inputs together:

resolved effort	cap	result
none	Low	Low
None	Low	None (explicit, below cap)
Low	Low	Low
High	Low	Low (lowered)
anything	cap off	unchanged

The existing invariant holds: the cap never raises effort, and an explicitly lower effort is preserved. The doc comment on compact_effort_cap is updated to state that a missing effort now takes the cap too.

Verification

• New test compact_effort_cap_defaults_a_missing_effort covers every row above
• Existing compact_request_downgrades_effort_to_cap and compact_effort_cap_parses_env_values unchanged and passing
• cargo clippy --all-targets -- -D warnings clean, cargo fmt --check clean, full suite green

🤖 Generated with Claude Code

[raine]

Thanks for catching the missing-effort case! Merged.