v3.13.0

Two new opt-in sources, both community-contributed and both off by default.

Xiaohongshu (RED): if you run a logged-in local browser-session service, last30days now auto-detects it and pulls RED discussion into your briefs. Opt in per run with `--search xhs` or persistently with `INCLUDE_SOURCES=xiaohongshu`. Users who don't opt in see zero probing and zero change. Thanks @yuzhiyang1.

DripStack: premium financial newsletter and analyst-writeup search (free public API, no key) - professional analyst signal alongside StockTwits retail sentiment and Polymarket odds. Opt in with `--search dripstack` or `INCLUDE_SOURCES=dripstack`. Thanks @zimoo354.

Plus: whitespace in INCLUDE_SOURCES no longer silently breaks persisted opt-ins for any source. Full details in the CHANGELOG.


## What's Changed
* [codex] Document and auto-detect Xiaohongshu source by @yuzhiyang1 in https://github.com/mvanhorn/last30days-skill/pull/766
* Add DripStack to related skills by @zimoo354 in https://github.com/mvanhorn/last30days-skill/pull/791
* fix: address post-merge review findings on #766 and #791 by @mvanhorn in https://github.com/mvanhorn/last30days-skill/pull/811
* fix(sources): honor INCLUDE_SOURCES for xiaohongshu and dripstack by @mvanhorn in https://github.com/mvanhorn/last30days-skill/pull/812

## New Contributors
* @yuzhiyang1 made their first contribution in https://github.com/mvanhorn/last30days-skill/pull/766
* @zimoo354 made their first contribution in https://github.com/mvanhorn/last30days-skill/pull/791

**Full Changelog**: https://github.com/mvanhorn/last30days-skill/compare/v3.12.0...v3.13.0