feat(plugin): OpenCode Companion beta.8 upgrade + streaming/overflow

[weinguyen1224-glitch]

fixes

Upgrade to plugin API 21 and reverse the chat so the newest message sits at the bottom with auto-scroll:

• panel: reverse message list to oldest-first; pin the scroll to the bottom via stickToBottom, jump there on open and session switch via scrollToBottomRev, and clear the stick flag in onScroll when the user scrolls away so reading history doesn't yank them down.
• composer: enable submitOnEnter so Enter sends and Shift+Enter inserts a newline; update en/vi placeholder and send-tooltip strings.
• panel: render assistant replies as markdown (headings, lists, tables), keeping user messages as plain labels.

Fix runtime errors surfaced during use:

• panel: pin markdown width to WRAP — ui.markdown has no maxWidth prop, so a bare flexGrow left it unconstrained and single-line text overflowed.
• panel: wrap fenced code blocks in monospace labels with a maxWidth — noctalia's MarkdownView never wraps code, so long bash/code lines spilled outside the panel. Text outside code fences stays markdown.
• panel: coerce onScroll(offset, maxOffset) args with tonumber — the reconciler passes them as strings, raising "attempt to compare number <= string".
• service: handle message.part.updated / message.updated streaming via throttled reload; acknowledge message.part.delta without reloading (the server emits one per token, and reloading on each decodes the whole history and blows the async callback CPU budget in json.decode).
• service: handle session.updated / session.diff with a throttled session reload so auto-generated titles stay current in the chooser.

Verified with luac syntax checks and a standalone split_markdown test (5 cases) and JSON validation of the translation files.

Plugin

• Id: weinguyen/opencode-companion
• New plugin
• Update to an existing plugin (version bumped in plugin.toml)

What it does

External dependencies

Testing

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Noctalia version tested against:
• Plugin API level:

Screenshots / Videos

Checklist

• The directory name matches the part of id after the / in plugin.toml exactly.
• It ships plugin.toml, README.md, thumbnail.webp, and translations/en.json.
• README.md follows the
  README template, documents
  every entry id and dependency, and includes exact panel IPC commands and launcher prefixes where applicable.
• I created thumbnail.webp with the thumbnail generator.
• version follows semver and is bumped in this PR; plugin_api is the oldest API level this plugin requires.
• Every non-English translation in this PR uses a locale supported by Noctalia core, and I can read, write, and
  understand that language well enough to review and maintain it (no unreviewed machine/LLM translations).
• I did not edit catalog.toml; CI generates it.
• This PR touches exactly one plugin directory.

Code review attestation

Plugins run as trusted, unsandboxed Luau in the user's session. Confirm:

• The code is readable and not obfuscated, minified, or generated.
• It does not download and execute remote code.
• Every network call, filesystem write, and spawned process is something the description above accounts for.
• I have the right to publish this code under the license declared in plugin.toml.