docs(search): describe the command palette's record search

docs/README.md

@@ -34,6 +34,10 @@ notes, and machine-readable specs that ship alongside the source:
   managed profiles for somebody with no login and the guardians who look
   after them, what revocation does and does not undo, and which trust
   properties of the instance are unchanged by any of it.
+- [`using/`](./using/) — notes on using the app that sit close to the
+  code. [`using/search.md`](./using/search.md) covers the command palette's
+  record search: opening it, what it finds, how matching works, and its
+  limits on very large and shared records.
 - [`migration/`](./migration/) — migration notes. Currently only
   v1.3 to v1.4; later releases are covered by `CHANGELOG.md` and
   <https://docs.healthlog.dev>.

docs/using/search.md

@@ -0,0 +1,55 @@
+# Searching your record
+
+The command palette finds pages and settings, and it searches what you have
+recorded.
+
+## Opening it
+
+Press **⌘K** on a Mac or **Ctrl K** elsewhere, or tap the magnifier at the
+top right, and start typing.
+
+## What it finds
+
+Below the pages and settings, a section **In your records** lists the
+entries that match what you typed:
+
+- visits (procedures included)
+- conditions
+- documents, by title, file name and the text read from them
+- vaccinations
+- lab results
+- medications
+- symptoms
+- workouts
+- notes on mood entries, readings and illness days
+
+Each hit opens where the entry lives: a visit on the check-ups page, a lab
+result on its analyte, a note on a mood entry or a reading on its day, a note
+on an illness day in its illness.
+
+## How matching works
+
+Case and accents do not matter, so "schulter", "Schulter" and "Schülter"
+find the same entries. Umlauts can be typed as `ae`, `oe` and `ue` (and `ß`
+as `ss`), which helps on a keyboard without them.
+
+## Very large records
+
+The search reads each kind of entry newest first and stops after a fixed
+number of entries and a short time limit, so it stays quick on a record that
+holds years of data. When it stopped before reaching the oldest entries, the
+list says so. A more specific search term usually finds an older entry.
+
+## Shared records
+
+When someone has shared their whole record with you, the search works inside
+that record too. An account shared with you section by section cannot be
+searched: the search lays every section side by side, which a partial share
+does not open.
+
+## Privacy
+
+What you type is sent to your instance in the body of the request, not in the
+address, so it does not end up in a reverse proxy's access log or in the
+browser history. The server does not log the search text either, only its
+length and how many hits it found.