feat(mkcapsule): no upper bound on capsule block numbers

Blocks 0..2047, the VM's fast RAM, are the only ones a capsule may not
claim (docs/v4.0.0/NUCLEUS.md 5.2).  The ceiling of 5120 matched no device.
All 36 capsule files still lint clean.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

experiments/bare_metal/README.md

@@ -144,8 +144,10 @@ which block slot to fill.
 
 1. The first line of each logical block must be `Block NNNN` (capital B,
    single space, decimal integer).
-2. Block numbers must be unique within a single capsule file, and must fall
-   in `[2048, 5120)`.
+2. Block numbers must be unique within a single capsule file, and must be
+   2048 or more. Blocks 0–2047 are the VM's fast RAM and the only ones a
+   capsule may not claim; there is no upper bound (ruled 2026-10-05,
+   `docs/v4.0.0/NUCLEUS.md` §5.2 — previously `[2048, 5120)`).
 3. Blocks are loaded in file order and executed top-to-bottom.
 4. Each block can hold at most 16 content lines, each at most 64 characters
    long (`validate_forth_blocks` in `tools/mkcapsule.c`, corrected 2026-09-19