feat: use the application iconfeature/qaction-menus

The icon was committed in a previous session and referenced nowhere: no
qrc, no .desktop entry, no setWindowIcon. It is wired up now, as a window
icon, a desktop entry, and install rules placing both into hicolor and
share/applications.

resources.qrc belongs to the executable rather than to qtmaildir_lib. A
qrc compiled into a static library registers itself from a global
initialiser, and the linker discards that object because nothing
references it: the build succeeded, qInitResources_resources() was
present in the .a, and QFile::exists(":/icons/qtmaildir.svg") still
returned false at runtime. Verified loading at 16, 32 and 64 pixels after
the move.

Toolbar and menu actions take icons from the system theme by their
standard names, so they match the rest of the desktop rather than
shipping bespoke art. A theme lacking one leaves that action as text,
which still works.

1 files changed, 24 insertions, 2 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e0ff08b..c78cb94 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,22 @@ point at which they are stable.
 
 ### Added
 
+- Tags render as coloured chips instead of text in a column. The account tag
+  sits in front of the subject in the thread list, and the functional tags fill
+  a single row under the message pane, with anything that does not fit
+  collapsing into a `+N` chip whose tooltip names the rest.
+- `[tagcolors]` config group. Colours resolve by exact tag first, then by
+  top-level prefix, so one `shopping` entry covers `shopping/amazon` and
+  `shopping/nike` while `shopping/amazon` can still override its own. Built-in
+  defaults cover the usual state tags; anything unconfigured gets a stable
+  colour derived from its name.
+- `color` and `label` keys in an account stanza, setting the account chip's
+  fill and its text. `label` shortens a long key for display only and renames
+  nothing in notmuch; unset falls back to the key.
+- The application icon is now used: window icon, a `.desktop` entry, and
+  install rules placing both into `hicolor` and `share/applications`.
+- Toolbar and menu actions carry icons from the system theme, falling back to
+  text where a theme lacks one.
 - Menu bar covering every action: File, Edit, Message, View and Help.
 - Toolbar with the frequent subset, Sync, Archive, Delete and Undo.
 - **Help > Keyboard shortcuts**, listing the current bindings. Generated from
@@ -29,8 +45,14 @@ point at which they are stable.
   every column. The tag change was already applied, but `Tags` sat after the
   stretching `Subject` column and was pushed off-screen, so Delete looked like
   it had done nothing.
-- Thread list columns reordered to Tags, Date, From, Subject. Subject stretches
-  and is now last, so no column can be pushed out of view.
+- Thread list columns are Date, From and Subject, all resizable. The tags
+  column is gone: spelling out a dozen tags per row consumed most of the list's
+  width. Widening past the viewport scrolls horizontally rather than squeezing
+  the other columns.
+- Hierarchical tags in `[tagcolors]` were silently ignored. QSettings treats
+  `/` in a key as a group separator, so `shopping/amazon` becomes a nested key
+  that `childKeys()` never returns, and every tag containing a `/` fell through
+  to its prefix.
 - Three default bindings never fired. Typing a capital sends `Shift`+the key,
   but `N`, `F` and `G` were stored as the unshifted key, which no keystroke
   produces, leaving `toggle_unread`, `flag` and `sync` dead. A bare capital in