ContinuMail Converter v0.2.0 — Thunderbird profile conversion

Major feature enrichments — and a hard-won grudge against Mozilla Mork — ship with 0.2.0. The
headline is Thunderbird profile conversion.

ContinuMail Converter now reads Thunderbird's .msf / Mork metadata. Point it at a profile and
your full folder and subfolder tree comes across — and the per-message state the mbox alone throws
away (read/unread, stars, replied/forwarded flags, junk, and tags) is translated into native
MAPI properties (PID tags) and shows up natively in Outlook. Tags become Outlook categories
under your real Thunderbird tag names. It's paired with a scan-for-profiles step that
automatically matches every mail account and local archive with its .msf sidecar — no hunting for
files. This resolves the v0.1.2 "Thunderbird flags/starred not preserved" and "tags unsupported"
limitations for live-profile conversions.

New in 0.2.0 (CLI + GUI)

• Thunderbird .msf / Mork enrichment — read/unread, replied, forwarded, starred (→ follow-up
  flag), junk, and tags, recovered from a live profile and written as native MAPI properties.
  Degrades gracefully: an unreadable or mismatched .msf is skipped per-source and reported, never
  fatal.
• Tags → Outlook categories using your real tag display-names from prefs.js (non-ASCII included).
• Scan for profiles — auto-discovers Thunderbird profiles and pairs every mail account and local
  archive with its .msf sidecar; per-account detection (email / host) included.
• Multi-account → one PST per account by default (each account a top-level folder), with a
  "Combine into a single PST" toggle.
• Junk handling — leave / tag as a "Junk" category / move to a Junk Email folder.
• Drop expunged messages — optionally skip mail Thunderbird marked deleted but hasn't compacted
  out yet.
• Outlook category colours — import-colours (CLI) and a one-click card on the Done screen (GUI)
  push your Thunderbird tag colours into Outlook so the categories match.

On category colours and COM: category assignments live in the PST as MAPI properties (PID tags)
and need no Outlook. The Master Category List — the names-and-colours registry Outlook draws from
— does not live in the PST and can't be written from PID tags, so colour import drives Outlook
over COM to edit the CategoryList FAI message atomically (Windows only; Outlook installed and
closed). A --plan-file mode applies a previewed plan without re-scanning.

Hardening, security & other changes

• Mork reader — nested folders no longer read as empty. Real .msf files reuse a small numeric
  table id across scopes; tables are now keyed by the composite (scope, id), so enrichment no longer
  silently finds zero messages on real profiles.
• Mork reader — wider charset support (windows-1252, Shift-JIS, Big5, EUC-JP, via the runtime
  code-page provider) and more robust column-dictionary detection.
• import-colours fixes — correct bytes for non-ASCII categories (e.g. "ÆØÅ"); only shuts down an
  Outlook instance it actually started; excludes the NonJunk pseudo-tag from candidates.
• More mbox X-Mozilla-Status flags even without a profile — replied / forwarded / starred added
  to read/unread (POP / older Local Folders stores; no effect on flag-less IMAP/EWS exports) (#7).
• Faster large-folder writes — per-folder SaveChanges is batched at checkpoints instead of after
  every message. No behaviour change.
• GUI polish — real source count on the Scanning screen (was "0 files"); one box per account on
  the Source step (was "first@x +N more"); full-height rail with no sideways scroll; multi-account
  defaults to split; stepper Back-navigation reaches the Accounts step.
• Security — the vendored multi-string deserializer validates its item count with unsigned
  arithmetic against the buffer length before casting, turning a malformed/oversized count into a
  clean InvalidDataException instead of OverflowException/OutOfMemoryException.

Known limitations

• .msf enrichment needs a live profile (the mbox plus its sibling .msf). A bare exported
  .mbox still imports as before — only inline X-Mozilla-Status flags are recoverable, not
  tags / junk / expunged state.
• import-colours is Windows-only and needs Outlook installed and closed. Conversion itself still
  requires no Outlook — only tag colours do.

Internal

• New from-scratch, read-only Mork (.msf) reader (src/Mail2Pst.Core/Mork/) with enrichment
  built on top (src/Mail2Pst.Core/Msf/); extensive unit + env-gated real-corpus tests.
• Pure, COM-free, unit-tested category-colour XML/stream helpers extracted from the colour-import path.
• Desktop helper extractions (account grouping, PST-name sanitization/de-dup, output-path join,
  discovery parsing) and the single public-primary repo migration with a leak-check safety net.