Claude review: lib/fonts: Store font data as font_data_t; update consoles

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

This is the most substantial structural change. Introduces `font_data_t` as a typedef for `const unsigned char`, documents the hidden header layout, changes `struct font_desc.data` and `struct fbcon_display.fontdata` to `font_data_t *`, and adds the `font_data_buf()` accessor.

The hidden header documentation is excellent and very helpful:
```c
 * +------+-----------------------------+
 * | -16  |  CRC32 Checksum (optional)  |
 * | -12  |  <Unused>                   |
 * |  -8  |  Number of data bytes       |
 * |  -4  |  Reference count            |
 * +------+-----------------------------+
 * |   0  |  Data buffer                |
```

Minor documentation typos:
- `"fotn data"` should be `"font data"`
- `"characer count"` should be `"character count"`

The condition change in `fbcon_set_disp()` from `if (!vc->vc_font.data)` to `if (!p->fontdata)` is semantically correct since `p->fontdata` is now the authoritative source and `vc_font.data` is derived from it.

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