Fix spawn placement under the top bar, add per-window minimum sizes, and clean up maximize

Four reports after restarting into today's build, with a screenshot. The
screenshot was measured, not eyeballed: top bar y=0..29, a 4px accent border
at y=30..33, titlebar from y=34, bottom border at y=1027..1030, and 49px of
bare desktop below it.

Windows spawning too close to the top bar. A remembered position was
validated only by asking whether it landed on some monitor's full_geometry,
which includes the strip a top bar reserves, so an app whose remembered y was
small reopened with its titlebar under the bar. That is why it was
"sometimes": it depended on the stored value, and the live store holds
wezterm at y=44 and firefox at y=69 against a 30px bar. Remembered positions
are now clamped into the monitor's usable area.

Placement not surviving a logout. Window memory does persist, but five of the
eleven entries in the live store were saved with a second monitor attached,
at x >= 2000. Those points match no current monitor and were discarded
outright, falling back to a fresh cascade, so those apps appeared to remember
nothing. Such a position is now clamped onto a monitor that exists instead.

Per-window minimum sizes. One global floor is wrong in both directions.
Three sources now, in increasing precedence: the global floor, the client's
own declared minimum (xdg_toplevel.set_min_size or ICCCM hints), and a
min_width/min_height window rule overriding both. A rule wins permanently --
the backend refreshes the client's declared minimum on every decoration
redraw and must not undo a deliberate override.

Maximize, three faults in one report. A maximized window now draws no
border: its edges are the screen's edges, and the only place maximize stops
short is the bar strip, which is exactly where the measured line was.
maximize_geometry_for no longer subtracts a bottom-anchored dock's exclusive
zone, so maximize runs to the bottom of the screen and the dock floats over
it; top, left and right are still honoured.
general.maximize_covers_dock = false restores the old behaviour. With the
border gone the window sits flush under the bar instead of with an accent
line crowding it.

Verified: seven new tests on the real numbers from the live store, and
maximize geometry measured live in a nested instance (a window maximized on a
split half reports exactly that half's rect). NOT confirmed on screen: the
border removal and the dock behaviour - the nested backend has no bar or
dock to reserve a zone, and an attempt to check the border produced a failing
control, since srd set border_width only affects windows created after it.

515 tests pass, clippy clean.

2 files changed, 21 insertions, 0 deletions

diff --git a/crates/config/src/engine/general.rs b/crates/config/src/engine/general.rs
index c10ecf0..c8a136f 100644
--- a/crates/config/src/engine/general.rs
+++ b/crates/config/src/engine/general.rs
@@ -172,6 +172,23 @@ impl Engine {
                     _ => None,
                 }
             };
+            // `min_width`/`min_height` - the smallest this window may be
+            // resized to, overriding whatever the client itself declared.
+            // Two plain numbers rather than a `"WxH"` string: unlike an
+            // aspect ratio, a size is not conventionally written as one
+            // token, and `width`/`height` above already set the precedent
+            // for separate keys.
+            let min_size: Option<(u32, u32)> = {
+                let min_width: Option<u32> = actions.get("min_width")?;
+                let min_height: Option<u32> = actions.get("min_height")?;
+                match (min_width, min_height) {
+                    (None, None) => None,
+                    // One alone is meaningful - a terminal that needs
+                    // width but no particular height, say. The unset axis
+                    // keeps the global floor.
+                    (w, h) => Some((w.unwrap_or(srdwm_core::MIN_WINDOW_WIDTH), h.unwrap_or(srdwm_core::MIN_WINDOW_HEIGHT))),
+                }
+            };
             // `aspect_ratio = "9:16"` - the "phone monitor / special
             // workspace" ask's own real, scoped answer (see `Window::
             // aspect_ratio`'s own doc comment in `crates/core`): a rule
@@ -210,6 +227,7 @@ impl Engine {
                     opacity: actions.get("opacity")?,
                     resize_margin: actions.get("resize_margin")?,
                     aspect_ratio,
+                    min_size,
                 },
             };
             state.borrow().wm.borrow_mut().add_rule(rule);
diff --git a/crates/config/src/engine/support.rs b/crates/config/src/engine/support.rs
index a2423d2..76bcf5e 100644
--- a/crates/config/src/engine/support.rs
+++ b/crates/config/src/engine/support.rs
@@ -182,6 +182,9 @@ pub(super) fn default_config() -> HashMap<String, ConfigValue> {
     // Re-read `init.lua` when it changes on disk, no reload key needed.
     // See `main.rs`'s `config_mtime`/`CONFIG_POLL_INTERVAL`.
     set("general.config_reload_on_write", Bool(true));
+    // Maximize runs to the bottom of the screen, under a dock, rather than
+    // stopping above it. A top bar is still always honoured.
+    set("general.maximize_covers_dock", Bool(true));
     set("general.smart_placement", Bool(true));
     set("general.window_gap", Number(8.0));
     set("general.animations", Bool(true));