Problem

Introduced in PR #2066. The test module subgoal_extraction_tests in
crates/zeph-core/src/agent/context/summarization.rs (line 3520) calls
parse_subgoal_extraction_response() which is gated with
#[cfg(feature = "context-compression")] (line 3466).

However, the test module itself has no feature gate, causing a compilation
error when running tests without --features full:

error[E0425]: cannot find function `parse_subgoal_extraction_response` in this scope
   --> crates/zeph-core/src/agent/context/summarization.rs:3527:22

Reproduction

cargo nextest run --config-file .github/nextest.toml --workspace --lib --bins
# Fails with E0425

Expected

Tests should compile cleanly regardless of feature set. The fix is to add
#[cfg(feature = "context-compression")] to the subgoal_extraction_tests module.

Verified broken on

main @ bc1dd9c5 (PR #2066)

Fix

#[cfg(test)]
#[cfg(feature = "context-compression")]
mod subgoal_extraction_tests {
    ...
}

Severity: Medium (CI passes with --features full, but bare cargo test fails)