Forward Claude Code and goose inference to the agent gateway natively - #2916

## Summary

These are fixes for three browser-journey flakes that are failing open
PRs which don't touch the code under test. The change is test-only. No
browser cases are added or removed, and no assertion is relaxed.

The red `Browser journeys (chromium, 3/9)` / `(webkit, 4/14)` shards on
most open PRs come from a different problem:
`sidebar-geometry.spec.mjs:224` is broken on main. #2945 and #2946
already fix it, so this PR leaves it alone.

### 1. `channel-completion.spec.mjs`: cold dev-server load timed out

**Evidence:** `Flake check` on #2935 failed
`channel-completion.spec.mjs:7` on both engines with `page.goto: Timeout
15000ms exceeded` on
`/tests/fixtures/mentions.html?channels&stream&test-controls`
([chromium](https://github.com/block/buzz-app/actions/runs/42317084302/job/128232679087),
[webkit](https://github.com/block/buzz-app/actions/runs/42317084302/job/128232678918)).
#2935 doesn't touch that page.

**Cause:** this is the same cold load #2776 fixed for
`mentions.spec.mjs`. Each test here started its own Vite dev server for
the same ~1,600-module fixture.

**Fix:**
- `beforeAll` builds `mentions.html` once and serves it with
`build`/`preview`, using the same config as `mentions.spec.mjs`.
- The build keeps the dev server's CSS. Tailwind's optimizer and Vite's
CSS minifier each round the 20/14 line-height token to `1.42857`, so
line boxes become `19.99998px`. In WebKit that put the popup `4.03125px`
above the composer, and the test asserts exactly `4`. I confirmed this
locally: it fails 5/5 with either setting left on and passes with both
off. Turning both off keeps the geometry the test checked before.

### 2. `profiles.spec.mjs:940`: reopening Members right after closing
the profile

**Evidence:** `Flake check (webkit, 8/9)` on #2909 failed in repeat 8 of
10
([job](https://github.com/block/buzz-app/actions/runs/42313241314/job/128219877861)).
The trace shows this sequence:
1. `Escape` closes the profile panel.
2. Focus returns to "Manage members of One" within 40ms.
3. `Enter` is pressed 10ms later.
4. The DOM after that `Enter` shows the Profile panel again and no
Members dialog, so the next `row.click` times out.

**Fix:** after each `Escape`, wait for the address to leave the profile
(no `"detail"` in the `#buzz=` hash) before reopening Members. This is a
lifecycle barrier, not a delay. One step in this test already waited for
the panel to unmount before reopening; the other steps didn't wait at
all.

**Product follow-up (not fixed here):** the order of a dismissal's
history return and a quick reopen matters.
- If I delay `history.go` by 300ms, the unpatched test takes a different
path: the dismissal's `go(-1)` never runs, and the URL stays on the
profile visit under the reopened dialog.
- A `browser-history` unit sketch (deferred traversal: `push(channel)`,
`push(panel)`, `dismiss([panel])`, then `push(settings)` before the
traversal commits) lands on `channel`. The new `settings` visit is
undone.

Someone who owns navigation should decide whether a push during a
pending dismissal return should be deferred or replayed. That is a
navigation-history change, not a test fix.

### 3. `timeline.mjs` `edge()`: one wheel gesture stopped short

**Evidence:** `Browser journeys (webkit, 6/14)` on #2937 failed
`history-prefix.spec.mjs:37` with `wheel reaches timeline edge`,
`Received: 199`
([job](https://github.com/block/buzz-app/actions/runs/42320781857/job/128244819852)).
The trace shows the one `-3251px` wheel ended with `scrollend` and the
geometry then held still, so the poll could never pass.

**Fix:** `edge()` repeats the gesture, at most four times, until the
edge is reached. Every extra gesture must reduce the distance, so an
immobile timeline still fails. `upper()` already follows this rule. The
case of already being at the edge is unchanged: it still sends one small
wheel so production can start paging.

## Not in this PR, from the same survey of the 40 most recently updated
open PRs

- `sidebar-geometry.spec.mjs:224` (Drafts & sent row) is broken on main
since #2733 + #2728 crossed. #2945 is green and #2946 is in CI; either
one fixes it.
- `solo-chats.spec.mjs:322` (Share, webkit, on #2927) is being handled
in draft #2933.
- `layout.spec.mjs:803` on #2916 is already fixed on main by #2750.
#2916's merge ref predates it.
- #2911 (thread virtualization) and #2918 (per-channel notifications)
fail consistently in tests their own changes reach, so those look like
regressions for their authors, not flakes.

## Validation

All runs were local on macOS with
`tests/browser/playwright.ci.config.mjs` and `--no-deps`. These are not
hosted CI measurements.

- `channel-completion.spec.mjs`, `--repeat-each=5`, both engines: 20/20
passed with the change. Before the CSS settings were added, the built
fixture failed WebKit 5/5 (`4.03125`).
- `profiles.spec.mjs:940`, `--repeat-each=24 --workers=6`, WebKit:
passed. It also passed with `history.go/back/forward` delayed by 300ms,
in both engines.
- `history-prefix`, `history-loading`, `scroll`, `timeline-setup` and
`new-message-boundary` (all callers of `edge()`/`end()`), both engines:
70/70 passed.
- Full `history-prefix`, `channel-completion` and `profiles` files, both
engines: 43/44 passed. The one failure was `profiles.spec.mjs:6` in
WebKit, a test this PR doesn't touch. It then passed 4/4 both with and
without this change.

**Deferred and remaining gaps:**
- I couldn't reproduce the cold-load timeout or the WebKit stopping
short locally, so I have no local fail-before for those two. The
evidence is the CI traces linked above.
- The other `edge()` callers (24 spec files) are left to CI.
- A green run doesn't prove these flakes are gone.

Signed-off-by: Bradley Axen <[email protected]>
Co-authored-by: mbot <3754f8729004d95654c46dbab3129e4ab9ef05cc2534e2a3fbfc155983bd637b@buzz.block.builderlab.xyz>

…claude-neutral

Brings coder3's #2479 rework (8c7f436) up through #2916.

* origin/coder1/dxa-1156-host-forwarding:
  fix(pi): keep Pi's own model onboarding in gateway mode

Co-authored-by: Coder1 <db50ef1f1688dc7f3e536c17351e8e994a7466bcbe009794f61d64355c0ffc2e@buzz.block.builderlab.xyz>
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Signed-off-by: Philip Azar <[email protected]>

Brings in #2479's Pi rework through #2916 and #2917: Pi's own model
onboarding in gateway mode. Only Pi files and the removed gateway
Settings fixture change here.

Co-authored-by: coder2 <4acc49cb93576448ba82e631688c51a40bf03d6a889d78fddf57917d198de10f@buzz.block.builderlab.xyz>
Co-Authored-By: Claude Opus 5.5 <[email protected]>
Signed-off-by: Philip Azar <[email protected]>