perf: the console's constants move to flash, -378 B and -214 B of RAM

8382 -> 8004 B of flash, 725 -> 511 B of RAM on a part that has 2048.

The command names were a std::to_array of string_view, and on a Harvard
machine that is the worst of both: the characters land in .data and so does
the table's own pointer-and-length pair for each of them, so the firmware
carried 216 B of RAM for thirteen words that never change - and paid for them
in flash too, since .data is copied out of an initialiser image at startup.

They are one NUL-separated blob in flash now, walked with lpm. Separators
rather than an offset table, because an offset table is the RAM this exists to
give back; the names sit in it in match order, so the walk that finds a name
is the same walk that compares it and measures it. Flash falls further than
RAM does: the initialiser image and the two tables were 216 B of it, and the
blob is 87.

The header said the names "cannot" be in flash because they are matched at run
time. Being matched at run time is not a reason to be in RAM on a machine with
two address spaces - only being *written* is, and nothing writes these.

Two smaller things came with it. `reset`'s exact-match rule was a bool on
every entry to protect one; it is an index found by searching the list, so
reordering the commands cannot move the protection onto a different one. And
`version` was the last string_view left, holding its own characters and a
pointer to them.

The matching is now pinned rather than assumed: lookup() is constexpr and the
battery asserts the load-bearing order the README documents - `s` is show and
not statistics, `st` is statistics, no abbreviation of `reset` resolves, and
`helpful` is not `help`. Red-checked by claiming `s` is statistics.

Both modes byte-identical, ten tests green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

test/consteval.cpp

@@ -6,6 +6,7 @@
 #include <cstdint>
 
 #include "curve.hpp"
+#include "terminal.hpp"
 #include "thermistor.hpp"
 
 namespace {
@@ -81,4 +82,39 @@ consteval bool thermistor_falls()
 }
 static_assert(thermistor_falls());
 
+// The console's one parsing rule, read out of the flash blob the names live
+// in. Every case here is a property of the *order* the names sit in, so this
+// is what an edit to that list has to answer to.
+using app::terminal;
+
+// Full names, and the ends of the list - a walk that miscounts a separator
+// lands on a neighbour rather than failing, so both ends are named.
+static_assert(terminal::lookup("help") == 0);
+static_assert(terminal::lookup("save") == 12);
+static_assert(terminal::lookup("bootloader") == 4);
+
+// Abbreviations resolve to the first entry they prefix. `s` prefixes show,
+// statistics, set and save, and show is first - which is the original's
+// behaviour and the reason the list is ordered rather than sorted.
+static_assert(terminal::lookup("s") == 1);
+static_assert(terminal::lookup("st") == 6);
+static_assert(terminal::lookup("se") == 9);
+static_assert(terminal::lookup("sa") == 12);
+static_assert(terminal::lookup("up") == 5);
+static_assert(terminal::lookup("b") == 4);
+
+// `reset` is the exception: it must be typed in full, so no abbreviation of it
+// resolves - and none of its prefixes names anything else either.
+static_assert(terminal::lookup("reset") == 8);
+static_assert(terminal::lookup("rese") == terminal::no_command);
+static_assert(terminal::lookup("res") == terminal::no_command);
+static_assert(terminal::lookup("r") == terminal::no_command);
+
+// Nothing, and nothing that matches.
+static_assert(terminal::lookup("") == terminal::no_command);
+static_assert(terminal::lookup("xyzzy") == terminal::no_command);
+
+// Longer than the name it prefixes is not a match: `helpful` is not `help`.
+static_assert(terminal::lookup("helpful") == terminal::no_command);
+
 } // namespace