news digest (spec-013): rss/atom -> {news} file via cron

Replaces the broken pre-1.0-openai news_feed.py. Stdlib parsing with
defusedxml (feeds are untrusted XML), titles sanitized (SAF-03), feed
URLs SSRF-guarded. CLI: python -m fjerkroa_bot.news --config <cfg>.

specs/SPEC-013-news.md

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+# SPEC-013 — News digest
+
+Replaces the broken pre-1.0-openai `news_feed.py`. A CLI
+(`python -m fjerkroa_bot.news --config <cfg>`) fetches the
+`news-feeds` and writes a compact digest to the `news` file that
+`AIResponder.message` injects into the `{news}` slot. Feeds are
+external input and operator-configured.
+
+### NEWS-01 — RSS and Atom parse to items (coverage: test)
+
+`parse_feed(bytes, label)` extracts `{title, link, source}` from both
+RSS (`<item>`) and Atom (`<entry>`) documents, tolerates malformed
+XML (returns an empty list, logs), and never raises.
+
+### NEWS-02 — Digest is sanitized and bounded (coverage: test)
+
+`render_digest` caps at `news-max-items`, and every headline passes
+`sanitize_external_text` (SAF-03) — a feed cannot inject `@everyone`
+or control characters into the prompt via a headline.
+
+### NEWS-03 — Feeds are SSRF-guarded and deduped (coverage: test)
+
+`NewsFetcher.collect` skips any feed URL the SSRF guard rejects,
+skips feeds that fail to fetch (one bad feed never sinks the run),
+and drops duplicate headlines across feeds.