breadclip: document pin verb, config file, and ignore rules

- EVENTS.md: `bread.command.clip.pin` and `bread.clip.pinned` /
  `.pin.failed` are now implemented; `select` stays explicitly not
  implemented with the reason. AGENTS.md follows.
- README: Configuration section, Ctrl+P bind, updated privacy notes
  (CLIPBOARD_STATE + ignore rules), JPEG image entries, primary badge.
- check.yml also runs on pushes to `main` — a push to main triggers a
  dev-track release build, so it should be linted/tested first.
- release.yml uses `${GITHUB_REPOSITORY}` instead of a hard-coded
  `Breadway/breadclip` for the GitHub mirror release upload.

contrib/config.toml.example

@@ -0,0 +1,24 @@
+# breadclip configuration — copy to
+#   $XDG_CONFIG_HOME/breadclip/config.toml   (usually ~/.config/breadclip/config.toml)
+#
+# Every key is optional; a missing file, missing key, or out-of-range value
+# falls back to the default shown here. A config file that fails to parse is
+# backed up to config.toml.bak once before defaults are used.
+
+[retention]
+# Max non-pinned entries kept per kind; the oldest are trimmed automatically.
+# 0 means "keep no (unpinned) entries of this kind". Pinned entries are never
+# trimmed, regardless of these caps.
+text = 200
+images = 50
+
+[panel]
+# Popup panel width in pixels.
+width = 520
+
+[capture]
+# Also watch the middle-click "primary" selection (wl-paste --watch --primary)
+# and store those entries alongside regular clipboard entries with a
+# "primary" badge. Off by default because primary selections tend to be
+# transient and noisy.
+primary = false