Messages: Push (repost) and Quote

[Adron]

Stacked PR — base is issue-127-wire-types, not main

This is the first of three stacked PRs (#31 → #32 → #33), all of which touch
FeedView.xaml / FeedViewModel.cs / MessageItemViewModel.cs.

It is based on issue-127-wire-types (open PR #131) because it depends on
the Message wire fields that branch adds — PushedMessageId, PushedMessage,
PushCount, and the IsPushOrQuote / IsQuote helpers. Merge #131 first, then
this.

What this does

POST /api/messages takes a pushedMessageId. One field covers both product
behaviours: a Push is a repost with empty content, a Quote is the same
call with commentary. Both are always public per /help/messages.

Service — Services/InterlinedApiClient.cs is untouched (it is in open
PR #130), so the write path is a new overload in the Messages partial:

• Models/NewMessage.cs — a request record for POST /api/messages. The
  positional overload had run out of room (reply, schedule, media, cross-post,
  and now push/quote and tags). Optional keys the caller never set are omitted
  rather than posted as explicit nulls.
• PostMessageAsync(NewMessage, …), plus PushMessageAsync /
  QuoteMessageAsync which hard-code publiclyVisible: true — that is a product
  rule, not the user's preference (defaultPubliclyVisible is false on the
  test account, so this is a real difference).

ViewModel — PushCount, the IsPush / IsQuote split, the quoted-original
projection off the nested pushedMessage, and the Push / Quote commands. A
Posted event lets FeedViewModel re-fetch after publishing, since the write
envelopes are not parsed (this codebase's read-after-write discipline).

View — ↻ Pushed / ❝ Quoted badge, the embedded original (avatar,
clickable author → profile, time, body, images), pushCount beside digCount,
and an inline Quote composer whose amber banner is the "this will be public"
confirmation. Two incidental fixes fell out of it:

• the card footer is now a WrapPanel — seven actions overflowed a narrow window;
• a per-card status line was added, because MessageItemViewModel.ErrorMessage
  had no renderer at all before this, so a failed action (or the "Reported.
  Thanks…" acknowledgement) was silent.

One deliberate client-side decision

Pushing a bare push targets the original rather than the push, so the
result is a one-level quote that actually renders instead of a chain of empty
cards. Quoting a Quote still targets the quote, which carries its own
commentary. No nested pushedMessage appeared anywhere in an 80-row live
sample, so the server's own chaining behaviour is unverified — this is the
client picking the renderable option, and it is commented as such.

Live verification (read-only)

Sampled GET /api/messages?limit=80 against the test account:

• 5 of 80 rows carry pushedMessageId plus a full nested pushedMessage (a
  complete message object, user included — no second fetch needed to render).
• Correction to the issue's note: 2 of those 5 have non-empty content —
  real Quotes, not only bare reposts. So the content-based IsQuote split is
  exercised by live data, not just theoretical.
• All 5 are publiclyVisible: true, consistent with the always-public rule.
• pushCount was non-zero on 6 of 80 rows, so the counter has real values to show.

Left unexercised, on purpose

No write path was run. Posting, pushing or quoting from this account
publishes publicly and syndicates to Mastodon/Bluesky, so PushMessageAsync,
QuoteMessageAsync and PostMessageAsync(NewMessage) are built and
live-unverified — the usual pattern in this repo. The request body follows
the same field names the existing positional PostMessageAsync already posts
successfully, with pushedMessageId added.

Notes for other open branches

Views/MentionText.cs (PR #141) will need a small reconcile: this PR adds a
Visibility binding to the card-body TextBlock (so a bare Push collapses its
empty body) on the same element PR #141 replaces the Text binding on. The
right rail in MainWindow.xaml (PR #149) is untouched.

Builds clean in both -c Debug and -c Release.

Closes #31

🤖 Generated with Claude Code

[Adron]

Auto-closed by GitHub when its base branch issue-127-wire-types was deleted on merge of #131 — my error for merging with --delete-branch while this PR still pointed at it. Recreated as #181 from the same branch and commits, now based on main. Nothing was lost; the diff is identical.

I've switched to merging without --delete-branch for the rest of this pass, and will clean up branches at the end once no PR depends on them.