v1.7.1

v1.7.1 — empty-search treatment, typed call graph, truncation wrap-up

Eval-driven review-quality release:
- code_search suggests real identifiers on zero hits (#73)
- ranked repo symbol map injected per run, Go+Python backends (#74-#76, #80)
- budget wrap-up turn + unit_incomplete marking (#77)
- code_comment keeps scope-member paths (#79)
- typed Go call graph for caller/callee clues and chain merge (#81, #82)
- eval/ methodology + codegraph design docs (#72, #83)

Measured: empty searches 60%→0 on worst-baseline PRs; caller
neighborhoods exact vs 5/8-wrong under grep.