docs: fix the docs that drifted from the code, add an architecture map and Vietnamese translations

[longvo92]

Why

The README described a tool that had moved on without it, and the one document a
newcomer most needs — how the pieces fit together — did not exist at all.

What changed

README corrections, each checked against the code rather than assumed:

• The viewer section never mentioned Export report… / Ctrl+E, including the
  guarantee that it is built from the complete scan and not from what is on
  screen.
• The module tree was missing view_model.py, syntax.py, review.py and
  gitsource.py — view_model.py is the seam that keeps the report and the
  viewer from disagreeing, and it was not named once.
• The add-a-rule note skipped a2l_rules.py, skipped the shadow step, and asked
  for "a test" where the rule checklist requires two — the pattern alone, and
  the same pattern beside a real change.
• --review did not say the badge hides changes already signed off.

docs/architecture.md — new: why the core is stdlib-only, what each of the
two diff passes decides, why the verdict lives in one function, what the result
dict guarantees downstream, and a "change X, touch Y" table.

docs/vi/ — Vietnamese README and architecture doc, for the team that reads
Vietnamese. Both say up front that the English files are authoritative, so a
stale translation cannot quietly become the thing someone trusts.

Stale facts fixed everywhere they appeared: build.ps1 has no -Exe switch
(the default builds the exe; -Pyz / -PyzOnly add or isolate the zipapp), the
smoke-render command in CLAUDE.md named a script that is not in the repo, and
the zipapp is ~110 KB — measured, not the 78–80 KB that README, CLAUDE.md and
build.ps1 all claimed.

Checks

• python -m unittest discover -s tests — 378 tests, OK.
• Every relative link in the four docs resolves.
• No behaviour change: the only non-doc edit is a size figure in a build.ps1
  comment.