feat(ai): stream explanations live (Ollama NDJSON + Claude SSE) — 0.33.0

ai.explain_stream(findings_text, on_chunk) streams token deltas and returns
(ok, full_text). Ollama: stream=True NDJSON; Claude: stream=True SSE (parse
content_block_delta text deltas). The diagnostic dialog opens an explanation
window immediately and fills it token-by-token via a _chunk signal, then
re-renders the finished answer as Markdown — no more multi-second freeze on a
local model. Non-streaming explain() kept for the CLI. Tests for both parsers;
verified live against qwen2.5:7b.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.33.0] - 2026-05-22
+### Added
+- **AI explanations stream live.** "Explain with AI" now fills token-by-token as the model
+  generates (Ollama NDJSON + Claude SSE, both via stdlib `urllib`) instead of a multi-second
+  freeze, then re-renders the finished answer as Markdown. `core/ai.explain_stream()`.
+
 ## [0.32.0] - 2026-05-22
 ### Added
 - **More for diagnostics & reports:**