slosh: defaults most people can live in, said by shaders

The out-of-the-box look, rethought as one piece:

- the compiled-in palette calms down: muted blue #7aa2f7 on the same
  neutral darks, with the colours that mean something kept semantic --
  amber bell, red-orange dead. sl0p stays one include away as the house
  style, and contrib/themes/default.kdl is the starting point written
  down (theme-tour shows it).

- derived state defaults now actually follow the theme: the scrolled
  wash is rebuilt from scroll_bg after the theme block (it used to bake
  the compiled accent), and declaring a state -- in any file of an
  include chain -- still wins. The dump writes derived states as
  comments so C-a e cannot pin what is meant to keep following.

- a bell you can see: the frame blinks three times in theme's bell
  colour then breathes until answered, and a soft diagonal shimmer --
  the bell colour halved towards default_fg, width breathing on a sine
  -- crosses the body for the same 900ms. bell_indicator false silences
  all of it; states { bell { } } replaces it like any state. since
  carries the clock dependency, so an idle session pays nothing.

- scrollback says where it continues: while scrolled, the viewport's
  top and bottom rows melt towards an edge with content past it and
  turn solid at the buffer's end. New expression variables above/below
  (lines hidden past each edge, own dependency bit, cached per scroll
  position), carried in shade_ctx_t -- SLOSH_SHADER_ABI 3 -> 4.

- expressions survive the dump: a program keeps its source and cb_chain
  writes it back, so amount="(y % 2) * 40" no longer dumps as a number.

- headers move to include/, -Iinclude everywhere; the plugin Makefile's
  SLOSH var becomes SLOSH_DIR because slosh exports SLOSH=1 into every
  pane it runs, and building from inside a session read that as a path.

- comment drift culled where features outran the prose, and the
  derivation boilerplate folded into derived_pass()/ctx_scroll().

1 files changed, 28 insertions, 0 deletions

diff --git a/include/server.h b/include/server.h
new file mode 100644
index 0000000..b5d114a
--- /dev/null
+++ b/include/server.h
@@ -0,0 +1,28 @@
+/* Server and client entry points. See proto.h for the wire. */
+#ifndef SLOSH_SERVER_H
+#define SLOSH_SERVER_H
+
+#include <stdbool.h>
+#include <stdint.h>
+
+#include "slosh.h"
+
+/* Run the session in this process (the daemonised half). `watch` re-reads the
+ * config when the file changes; see server.c for why that is a flag and not a
+ * config setting. */
+/* What panes are told about the session around them: its name, or NULL for a
+ * mode that has no socket, which must clear it rather than inherit a lie. */
+void session_env(const char *name);
+
+int server_run(const char *name, const char *const argv[], uint16_t cols,
+               uint16_t rows, const char *layout, bool watch);
+/* Fork a server, then wait for its socket to answer. Returns a connected fd. */
+int server_spawn(const char *name, const char *const argv[], uint16_t cols,
+                 uint16_t rows, const char *layout, bool watch);
+/* Connect to an existing session, or -1. */
+int server_connect(const char *name);
+
+int client_run(int fd);
+int client_control(int fd, const char *line);
+
+#endif /* SLOSH_SERVER_H */