Sync dev to main: page descriptions - #1103

* Stop publishing snippet fragments, and two small fixes

The 25 files under docs/_snippets are fragments that other pages pull in
via pymdownx.snippets. They were also building as standalone pages, so
they sat in the sitemap for Google to index and generated their own social
cards. One of them is a bare admonition with two buttons, presented to a
reader as a page. Exclude the directory from the build output. The
snippets extension reads these from disk through its own base_path rather
than through MkDocs' file collection, so every include still resolves.

Point the PLT-1B links in the two sensor connection check pages at the
plt1b pages. Both files label the links "PLT-1B reset button" and "PLT-1B
boot button" while pointing at plt1 paths, and both already use temp1b
paths for their TEMP-1B labels, so the -B variants are what these want.

Fix three spellings of "rechargable".

Verified with a full build: no _snippets page is emitted, the sitemap
carries zero _snippets entries, and all 49 pages that include a fragment
render its content with no raw snippet syntax leaking through.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

* Give every page its own description

Every publishable page now carries its own description, so no page falls
back to the site-wide sentence in a link embed or a search result. 688
pages, previously 303 of them had nothing of their own.

Most of this is not new prose. 178 of the pages are snippet wrappers whose
entire content is one include line, and they inherit the description of
the page they mirror, following the chain where one wrapper includes
another. Another 68 homey pages inherit from their main tree counterpart,
skipping any whose description names Home Assistant or ESPHome, since
those would be wrong on a Homey page. That left 59 written from the page
content: 28 in the main tree and 31 under homey.

Every description is quoted. An unquoted YAML scalar containing a colon
followed by a space parses as a mapping, which silently invalidates the
front matter and leaves the page on the fallback with no build warning.

Ten pages are included elsewhere whole, so their includers get a line
offset to skip the new front matter. Without it the front matter renders
as visible text on the including page.

Five includes pointed at files that do not exist, so those pages were live
and rendering empty. Three are repaired: the homey AIR-1 prevent sleep
page now pulls the general battery sensor page rather than a path that was
never there, the homey zone configuration page matches its main tree
equivalent, and the Odroid Bluetooth tracking page was missing the
products/ prefix. The other two, products/msr1/calibrating-co2 and
homey/products/mtr1/calibrating-co2, are removed. Both pulled a
co2-calibration-quick-mobile page that has never existed, neither is in
the nav, and both products already have a working CO2 calibration page.

The homey Our Team page pulled contact-us/general/our-team, another path
that does not exist, and rendered as a bare title. It now pulls the real
page.

Verified against a full build: no page emits the site-wide fallback, no
page leaks raw front matter or raw snippet syntax into its body, the
previously empty pages render their content, and the sitemap holds 688
URLs with the two removed pages gone.

🤖 Generated with [Claude Code](https://claude.com/claude-code)