docs(roadmap): restructure into per-topic tables + tri-state buckets

The flat checklist had grown to 267 lines of bullets that conflated
"not done yet, plus maybe later" with "needs a printer connection".
Restructure into per-topic tables with a Status column (`[x]` /
`[ ]`) plus a Bucket column that names the initiative each pending
command waits on:

  Coming soon              registry / parser work, no infra dep
  Modal: Media & Feed      lands with Printer Settings Modal Tab 1
  Modal: Print Quality     Tab 2
  Modal: Clock & Time      Tab 3
  Modal: Encoding & Lang   Tab 4
  Modal: Identity          Tab 5
  Native build             needs bidirectional printer connection

That separates the architectural "blocked on Tauri" answer from the
shippable "blocked on UI" answer, so it's clear at a glance how
much pure-emit coverage is still on the table without waiting for
the desktop build.

Content updates folded in:
  - ^BV (UPS MaxiCode) moved to Supported (PR #103)
  - ^BD noted as a firmware-generation alias of ^BV instead of a
    separate "coming soon" entry
  - ^GS moved to Supported (parser + symbol registry have shipped)
  - pure-emit hardware commands (^MN, ^ML, ^MF, ^XB, ^MA, ^MC,
    ^MI, ^MP, ^MU, ^MW, ^PA, ^JZ, ^JH, ^JT, ~TA, ^ST, ^SO, ^KD,
    ^KL, ^SE/~SE, ^SZ, ^KN, ^SL, ^KP, ^KV) re-bucketed from "Native
    build" into the Modal tabs, since they don't actually need a
    printer connection

Author: u8array