fix: adversarial review round 5 — release v0.1.7

[ejwhite7]

Summary

Addresses all findings from the round-5 code review of v0.1.6. Each fix has a regression test; the full suite passes (470 examples, 0 failures).

Severity	Finding	Fix
🔴 Critical	Compaction emitted an :assistant first message → Anthropic HTTP 400 ("first message must use the 'user' role") whenever the first preserved message was :user or the preserved window emptied	Summary is now always :user; merged into the first preserved message when that is also :user (no consecutive same-role); empty window → lone :user summary. Extracted to Compaction#build_compacted_history
🟡 Minor	Compaction "mirror case" branch was unreachable dead code (the preceding while guarantees preserved.first is never :tool)	Removed it and the redundant second droppable.empty? guard
🟡 Minor	Deterministic ProviderError (missing tool_call_id, invalid arg JSON — raised before any HTTP call) was retried through the backoff schedule	Removed ProviderError from the retry set; Fallback failover unaffected (rescues the RubyPi::Error superclass)
🟡 Minor	before_tool_call/after_tool_call hooks saw string-keyed args while events & tool_calls_made saw symbol keys	Loop#act rebuilds each ToolCall with symbol-keyed args once, so all consumers agree
🟡 Minor	Anthropic streaming finish_reason clobbered to nil by a trailing message_delta with no stop_reason	Guarded assignment, matching OpenAI/Gemini
🟡 Minor	Gemini finishReason.downcase assumed a String	Both paths coerce via to_s, now consistent
⚪ Cleanup	Dead streamed_content accumulator + inaccurate comment in Loop#think	Removed; :provider_fallback event still fires
⚪ Docs	Fallback class docstring still described removed happy-path buffering	Rewritten to describe direct streaming + :fallback_start

Investigated, no change

Streaming error bodies via env.status — verified against the actual stack (faraday 2.14.1 / faraday-net_http 3.3.0): the net_http adapter calls save_http_response (sets env.status) before response.read_body streams chunks, and Env#stream_response passes that same populated env to the on_data proc. env.status is reliably available before the first chunk, so the existing error_body recovery works. No fix needed — documented in CHANGELOG.

Testing

• New spec/ruby_pi/fixes/review_round5_spec.rb (9 examples) covering compaction ordering/merge/empty-window, retry policy (incl. an ApiError-still-retries control), Anthropic finish_reason, and Gemini finishReason robustness.
• New hook-key-consistency example in spec/ruby_pi/agent/loop_spec.rb.
• Updated two compaction_spec examples that encoded the old :assistant-first behavior.
• bundle exec rspec → 470 examples, 0 failures.

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