feat(web): read and reply to linked github discussions

[ashx-j]

linked github discussions currently open on github, away from the coding thread. this adds a discussion panel in web and desktop for reading comments and replies, posting markdown, reacting, upvoting, and changing labels or categories when the github account has permission. mobile keeps opening discussions on github.

this is the discussion reader/editor portion separated from #1. it is stacked on feat/snooze-until-github-reply, so this diff contains only the reader/editor and its integration. merge #1 first. the snooze behavior stays in #1.

github requests use the shared http api and quota handling. writes require source control write access, check the selected discussion before mutating, and update the client from github's confirmed response. closed discussion tabs can be reopened through the existing tab history. each operation pins the selected github account across permission checks and writes. locked discussions follow github's comment, reaction and voting permissions.

the reader fetches one bounded preview, up to 20 comments and 5 replies per comment. it shows full connection counts, labels partial sorting and participant counts, and links to the remaining posts on github. links to unloaded posts keep their original github destination. older servers without the separate reader capability continue opening discussions on github.

evidence

the before image was recaptured from #1 in a server-local browser against isolated development state. the after images and reply recording retain the original built-in browser captures with a local github fixture. the screenshots show #1 before this addition and the discussion panel after it. the reply recording uses mocked github responses and posts nothing to github.

before, no discussion panel	after, discussion beside the thread

short reply recording.

verification

163 tests pass in seven focused files on the integrated stack. they cover bounded reads, credential changes between permission checks and writes, locked and archived discussion permissions, confirmed-write counts, partial-preview anchors, older-server capability decoding, and thread management. server and web package typechecks pass. formatting and changed-file lint pass, with existing lint warnings remaining.

the images and recording above were captured before this review pass and show the same small-discussion flow. that earlier browser pass loaded the discussion and posted a fixture reply. fresh capture of the new partial-preview state was not completed because the built-in browser's automation host disconnected. native mobile and electron verification have not been run. github implementation checks remain queued on the fork's custom runners.

remaining upstream work

this is a fork prototype. explicit maintainer approval of the feature's direction and scope is still needed before an upstream submission.

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gpt 6 astra and gpt 6.1 sol in codex through t3 code, writing on behalf of ash.