build: the libavr pin advances past phase 6, at byte parity everywhere

The pin crosses libavr's phase 6 - the renamed system surface, the named
serial configs, the receiver-tolerance table, the paged SPM receipts -
and every loader image comes out size-identical: the full matrix on six
representative chips (the exhaustive cross product on three of them),
the stock and autobaud columns untouched, the four tsb tiers back on
their recorded floors at 510/526/638/836.

Byte parity was not free, and the two libavr defects it surfaced were
fixed there rather than absorbed here. The EEPROM write procedure's
step 2 - the SPMEN spin - had landed unconditionally and cost every
build six bytes for a wait a polled loader can never take; it is scoped
now, and the loaders state the datasheet's own omission clause
(spm_interlock::omitted, DS40002061B 8.6.3). The blocking page
erase/write grew an internal wait the tiers' settle() already provides,
so the tiers issue the command form and pureboot keeps its host-driven
sp_spm path.

What the port states rather than inherits: the stock 115200 at 16 MHz
sits +2.1 % past the receiver-tolerance table libavr now holds rates
to, so the hardware links say .allow_baud_error = true - the same
2.5 % envelope pureboot_baud_feasible() has always enforced, proven on
silicon across the fleet. rx_ready() reads readable() now.

Alongside the pin: rule 33's ASCII sweep over every source (docs keep
their typography), rule 34's InsertBraces in .clang-format with the
tree reformatted, std::array over the simavr runners' raw buffers, and
the stale Studio size in ide/README.md replaced by the claim its
check-flags gate actually holds.

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

tools/sizes.py

@@ -3,7 +3,7 @@
 
 The size matrix asserts every image fits its slot; it says nothing about the
 numbers the README prints, and those drift. Every row of that table was eight
-bytes stale once `startup::caller_page()` landed — common code, so every build
+bytes stale once `startup::caller_page()` landed - common code, so every build
 moved at once and no test noticed, because none of them was over budget.
 
 Two questions, both answered from built trees:
@@ -12,14 +12,14 @@ Two questions, both answered from built trees:
   sizes.py check-readme   the README's per-chip table against what is built
 
 Nothing here knows a chip's geometry. The (image, budget) pairs come from each
-build's own `CTestTestfile.cmake` — the same values the gate checks — so the
+build's own `CTestTestfile.cmake` - the same values the gate checks - so the
 slot rules stay where they belong, in `pureboot/CMakeLists.txt`, and a chip
 added or a budget changed needs no edit here. Only trees a configure preset
 still owns are read: a stale directory keeps its last build, and a loader built
 before a slot changed will happily report a size that was true once
 (`tools/prune-build-trees.sh` in libavr removes them).
 
-Sizes come from `avr-size`, and a target is only as current as its last build —
+Sizes come from `avr-size`, and a target is only as current as its last build -
 run the gate first if you want the table checked against today's source.
 """
 
@@ -33,7 +33,7 @@ import subprocess
 import sys
 
 ROOT = pathlib.Path(__file__).resolve().parents[1]
-# add_test(<name>.size ... -DELF=<path> ... -DLIMIT=<n> ...) — the gate's own
+# add_test(<name>.size ... -DELF=<path> ... -DLIMIT=<n> ...) - the gate's own
 # pairing of an image with the budget it must fit.
 # ctest writes the name as a bracket argument ([=[name.size]=]) and quotes the
 # rest, so the name starts after the bracket and the path ends at the quote.
@@ -56,7 +56,7 @@ def preset_dirs() -> list[pathlib.Path]:
     listing = subprocess.run(["cmake", "--list-presets"], cwd=ROOT, capture_output=True, text=True)
     names = re.findall(r'^\s*"(.+)"$', listing.stdout, re.MULTILINE)
     if not names:
-        sys.exit("cmake --list-presets returned nothing — run from a configured checkout")
+        sys.exit("cmake --list-presets returned nothing - run from a configured checkout")
     return [d for d in (ROOT / "build" / n for n in names) if (d / "CTestTestfile.cmake").is_file()]
 
 
@@ -86,7 +86,7 @@ def collect() -> dict[str, list[tuple[str, int, int]]]:
     sizes = measure([elf for rows in found.values() for _, elf, _ in rows], tool)
     # A chip's generated and reflect trees must answer with the same bytes
     # (the identity invariant), so the same target measuring two sizes means
-    # a stale tree — or an identity breach. Either is a finding; picking one
+    # a stale tree - or an identity breach. Either is a finding; picking one
     # silently is how a gate reports another build's numbers as today's.
     for chip, rows in found.items():
         seen: dict[str, tuple[int, str]] = {}
@@ -95,7 +95,7 @@ def collect() -> dict[str, list[tuple[str, int, int]]]:
                 continue
             if name in seen and seen[name][0] != sizes[elf]:
                 sys.exit(f"{chip} {name}: {seen[name][0]} B in {seen[name][1]} but "
-                         f"{sizes[elf]} B in {elf} — a stale tree (rebuild or remove it) "
+                         f"{sizes[elf]} B in {elf} - a stale tree (rebuild or remove it) "
                          f"or a cross-mode identity breach")
             seen.setdefault(name, (sizes[elf], elf))
     measured = {
@@ -111,7 +111,7 @@ def collect() -> dict[str, list[tuple[str, int, int]]]:
 def cmd_max(args) -> int:
     measured = collect()
     if not measured:
-        sys.exit("nothing built — configure and build a preset first")
+        sys.exit("nothing built - configure and build a preset first")
     over = []
     print(f"{'chip':<13} {'largest image':<34} {'.text':>6} {'budget':>7}  headroom")
     for chip, rows in measured.items():
@@ -129,7 +129,7 @@ def cmd_max(args) -> int:
     tightest = min(((chip, n, t, l) for chip, rows in measured.items() for n, t, l in rows),
                    key=lambda row: row[3] - row[2])
     chip, name, text, limit = tightest
-    print(f"tightest fit: {chip} {name} — {text} of {limit}, {limit - text} B spare")
+    print(f"tightest fit: {chip} {name} - {text} of {limit}, {limit - text} B spare")
     return 0
 
 
@@ -137,7 +137,7 @@ def cmd_check_readme(args) -> int:
     """The README's per-chip table, against the stock build and the worst
     autobaud configuration (OSCCAL baked, plus the USART-pin release where
     the chip has a USART; the one-wire fold of the same build is its twin
-    and competes for the same cell) — the config the Autobaud column
+    and competes for the same cell) - the config the Autobaud column
     documents."""
     readme = (ROOT / "pureboot" / "README.md").read_text()
     measured = collect()
@@ -147,7 +147,8 @@ def cmd_check_readme(args) -> int:
         sys.exit("no size table found in pureboot/README.md")
     bad = skipped = 0
     for chips, stock_doc, auto_doc in rows:
-        # "ATmega48, 48A, 48P, 48PA †" — the first name is the family's base.
+        # "ATmega48, 48A, 48P, 48PA" plus any footnote mark - the first name
+        # is the family's base, and the sub strips the rest.
         chip = re.sub(r"[^a-z0-9]", "", chips.split(",")[0].strip().lower())
         built = {name: text for name, text, _ in measured.get(chip, [])}
         # The on-USART pair defines the column where the chip has a USART;
@@ -167,7 +168,7 @@ def cmd_check_readme(args) -> int:
                 print(f"  {chip:<12} {target:<18} README says {documented} B, built is {built[target]} B")
                 bad += 1
     if bad:
-        print(f"\n{bad} row(s) stale — update pureboot/README.md")
+        print(f"\n{bad} row(s) stale - update pureboot/README.md")
         return 1
     print(f"README size table matches every built image ({len(rows)} rows"
           + (f", {skipped} not built" if skipped else "") + ")")