P6.x: read handler/provider given clauses via IR readers, not raw ast::CapRef

[accuser]

Summary

#1187 slice 1 of the follow-on completion plan: add lower_handler_given_ir (sibling of lower_provider_given_ir, bynk-emit/src/ir/lower.rs) and convert every given-consumption site that feeds a deps-type or cross-context decision to read the CapRefIr it produces, instead of walking bynk_syntax::ast::CapRef directly.

Converted sites:

• project.rs's plan_agent_given_deps and EmitProjectCtx::agent_method_givens
• emitter.rs's HandlerShared::agent_given_caps_used / record_agent_call / agent_given_caps_used() accessor
• emitter/emit.rs's effective_given, build_deps_object_ty_with_surface, cap_ref_ty (plus the provider given-to-deps-type call site, which now goes through lower_provider_given_ir too)
• emitter/workers.rs's worker_cross_caps

ast_importers stays at 8 — both emitter.rs/emitter/emit.rs/emitter/workers.rs were already counted for other reasons — but the real AST coupling at every one of these sites is gone.

Test plan

• cargo build --workspace
• cargo clippy --workspace --all-targets
• cargo fmt --all -- --check
• BYNK_BLESS=1 cargo test -p bynkc --test e2e bless_positive_fixtures — zero fixture diff
• cargo test -p bynkc --test tsc_verify — real tsc --strict, all 6 pass
• cargo test --workspace — full suite, including greenfield_status_table_is_current

🤖 Generated with Claude Code