Bump version to 0.2.0

[TroyHernandez]

Summary

Ready 0.2.0 for CRAN resubmission. The 0.1.0.1 dev marker is promoted
to a real minor release (additive features, backwards compatible).

• Version: 0.1.0.1 -> 0.2.0
• Date: 2026-05-13
• Description: added <https://element-hq.github.io/synapse/> after
  'Synapse' and <https://conduit.rs/> after 'Conduit' per the
  CRAN cookbook's "named external service needs an angle-bracketed
  URL" rule; dropped the bare 'mx.crypto' example (not on CRAN yet,
  no clean URL form).
• NEWS.md: heading renamed 0.1.0.1 -> 0.2.0. The list of
  changes already there describes the 0.2.0 delta accurately.
• cran-comments.md: refreshed for the update submission with the
  current check status (0/0/0) and the additive-only framing.

Pre-submission walkthrough

Walked the tinyverse pre-submission checklist; every section is clean
or correctly justified:

Section	Status
1. General (writes, network, platform)	No home-filespace writes; no network in tests; no platform assumptions
2. DESCRIPTION	Synapse/Conduit URLs added; Title / Authors / Imports clean
3. Code (T/F, <<-, cat/print, install.packages, setwd, set.seed)	Probe-clean
4. Documentation	Existing \dontrun{} disposition preserved with the same cran-comments justification CRAN accepted for 0.1.0; mx_session() and mx_canonical_json() have runnable examples
5. Resources	No new external resources
6. Local lessons (cornball.ai addenda)	No hidden Suggests, no global env mutation, no cat/print outside print methods

Verification

• tinytest::test_package("mx.api") -- 156 assertions, all pass
• tinypkgr::check() -- Status: OK (0 errors, 0 warnings, 0 notes)
• tinypkgr::check_win_devel() -- uploaded to R-devel
• tinypkgr::check_win_devel(r_version = "release") -- uploaded to R-release

Win-builder results email to troy@cornball.ai within ~30 minutes.
After this PR merges and the win-builder runs come back clean, Troy
runs tinypkgr::submit_cran() (Claude does not).

Why 0.2.0 right now

mx.crypto's security-audit-vignette PR depends on the new
mx_canonical_json() plus the four transport endpoints. Its CI is
currently red because the CRAN copy of mx.api is still 0.1.0.
Promoting 0.2.0 to CRAN clears that gate without resorting to a
Remotes: entry in mx.crypto.