refactor(context): ContextService::inject_semantic_recall is a dead public API — not called from any production path

[bug-ops]

Description

ContextService::inject_semantic_recall (zeph-agent-context/src/service.rs:203) is a pub async method with full tiered-retrieval logic and a 30s timeout, but it is never called from any production code path.

The only callers visible via grep are test helpers. Production context assembly goes through:

• ContextService::prepare_context → ContextAssembler::gather → fetch_semantic_recall (flat path), OR
• Agent::inject_semantic_recall (zeph-core/src/agent/context/assembly.rs:1351) — a separate shim that directly calls fetch_semantic_recall_raw without tiered retrieval.

This is the root cause of #3996: tiered retrieval is only reachable through ContextService::inject_semantic_recall, which is never wired into the agent turn loop.

Impact

• Tiered retrieval (MemFlow) never activates for any production session (confirms bug(agent-context): MemFlow tiered retrieval never activates in production — inject_semantic_recall not called from prepare_context #3996).
• Dead public API creates maintenance surface: future changes may incorrectly believe the method is already integrated.

Recommendation

Either:

1. Wire ContextService::inject_semantic_recall into the turn loop (fixes bug(agent-context): MemFlow tiered retrieval never activates in production — inject_semantic_recall not called from prepare_context #3996), or
2. Remove it and implement tiered retrieval inside ContextService::prepare_context / ContextAssembler::gather directly.

Environment

• Commit: c9ff16a
• File: crates/zeph-agent-context/src/service.rs:203
• Related: bug(agent-context): MemFlow tiered retrieval never activates in production — inject_semantic_recall not called from prepare_context #3996