console: a bare ESC[m is a reset, and OSC sequences are consumed

Two ANSI bugs, both found by running fastfetch rather than by reading the
parser, and both invisible to anything that spells its escapes out in full.

ESC[m with no parameters means ESC[0m. ECMA-48 is explicit that an omitted
parameter takes its default and SGR's default is 0, and sgr() iterated its
parameter list -- which is empty in exactly that case, so the loop body never
ran and the reset was silently dropped.

Programs emit the bare form constantly. fastfetch writes "\x1b[32m1%\x1b[m", so
everything after the first coloured character stayed green forever. With a
background colour it is much worse: its palette swatch sets a white background
and resets, the reset did nothing, and the console went white-on-white and
stayed there -- filling the screen with white rectangles as it scrolled, which
looks like a corrupted framebuffer rather than one missing branch.

OSC sequences were not a state at all, so ESC ] fell through and the payload
printed as text: a hyperlinked path arrived as "Disk (]8;;file:///\]8;;\)".
Nothing here acts on an operating-system command -- there is no window title and
no hyperlink to follow -- but *discarding* one is not optional, because the
alternative is printing somebody's URL into the middle of their output. ESC \
ends it, and an ESC followed by anything else is handed back to the escape state
rather than eaten, so a malformed OSC does not swallow the sequence after it.

Verified by screendumping the framebuffer after two consecutive fastfetch runs:
identical output both times, near-white coverage down from most of the screen to
2% (the palette swatch's own white cell), and the disk line reading "Disk (/)".

Also installs docs/branding/Ascii/ascii_50.txt as /usr/share/schos/logo.txt --
Shift as characters, at the width that leaves room for an info block on an
80-column console. Installed from the branding directory rather than copied into
sysroot by hand, so there is one source.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2

docs/architecture/graphics.md

@@ -129,6 +129,23 @@ what makes an OS look like a hobby project. Everything still goes out the UART.
 The console still uses the 8×16 cell grid. Porting it onto the text layer and
 deleting the grid is open work.
 
+Two things the ANSI parser got wrong until a large program nobody here wrote
+exercised it properly:
+
+**`ESC[m` with no parameters is a reset**, and `sgr()` iterated its parameter
+list — which is empty in that case, so the loop body never ran and the reset was
+dropped. ECMA-48 says an omitted parameter takes its default and SGR's default
+is 0. Programs emit the bare form constantly, so every colour set became
+permanent; with a *background* colour that meant the whole console went
+white-on-white and stayed there, which reads as a corrupted framebuffer rather
+than a missing branch.
+
+**OSC sequences must be consumed even when they are ignored.** `ESC ]` was not a
+state, so the payload printed as text and a hyperlinked path arrived as
+`Disk (]8;;file:///\]8;;\)`. There is no window title to set here and no
+hyperlink to follow, but discarding the body is not optional — the alternative
+is printing somebody's URL into the middle of their output.
+
 ### Input
 
 Keys reach both `/dev/input/eventN` and the tty line discipline, which is