chore: sync Mudlet runtime and spec corpus to c09c9427

[github-actions]

Automated re-sync of the vendored Mudlet trees — the Lua runtime and
default packages (sync:mudlet-lua) and the busted corpus that tests
them (sync:mudlet-specs), both pinned to the same upstream commit.

The spec corpus is a verbatim mirror, so a red run here is a parity
report, not a broken PR: it means Mudlet has specs for behaviour this
client does not match yet. Triage on this branch —

• yarn busted:failures re-runs only what failed;
• fix the gap, or record why matching would be wrong in
  e2e/knownDivergences.ts;
• a package that moved may need src/import/defaultPackages.ts updating —
  vendoring is not preinstalling, and a bumped archive needs its declared
  version bumped to match;
• commits pushed here survive: tomorrow's sync stacks onto this PR rather
  than replacing it;
• without push access, branch off chore/sync-mudlet-upstream and open
  your PR with that branch as the base, not master — merged there,
  the fix lands in this batch and tomorrow's sync stacks on top of it.
  Basing on master instead splits the triage across two PRs, and this
  one comes back red tomorrow.

_{Opened by .github/workflows/sync-mudlet-upstream.yml for #65. It
approves this PR's own ci.yml run and merges once that is green.}

---

 src/scripting/lua/mudlet-lua/SYNCED.md       |  2 +-
 src/scripting/lua/specs/CommandLine_spec.lua | 59 +++++++++++++++--------
 src/scripting/lua/specs/Mapper_spec.lua      | 70 ++++++++++++++++++++++++++++
 src/scripting/lua/specs/Networking_spec.lua  | 41 ++++++++++++++++
 src/scripting/lua/specs/Regex_spec.lua       | 27 +++++++++++
 src/scripting/lua/specs/SYNCED.md            |  2 +-
 src/scripting/lua/specs/UI_spec.lua          | 23 +++++++++
 7 files changed, 203 insertions(+), 21 deletions(-)