feat(link-previews): unfurl web links below messages by default - #3225

* origin/main:
  feat(messages): let attachment renderers open files from the host file card (block#2239)
  feat(charts): bundle a Charts code-block renderer (block#3226)
  Expose native reply grouping through Conversation.ui (block#3245)
  NEXUS-4163: Keep plugin-owned chat deletion in Solo (block#2787)
  NEXUS-4156: Expose Solo Workspaces to plugin regions (block#2786)
  NEXUS-4022: Start region chats in the New Chat editor (block#2784)
  feat(link-previews): unfurl web links below messages by default (block#3225)
  fix(messages): keep names in literal Markdown as written when editing (block#2834)
  feat(plugins): fetch a packaged managed plugin policy from a URL (block#2504)

Signed-off-by: Joah Gerstenberg <[email protected]>

# Conflicts:
#	crates/plugin-manager/tests/management.rs
#	docs/plugin-architecture.md

…y-untagged-reactions

* origin/main: (324 commits)
  fix(github): show private-repo body images from signed links (#3252)
  NEXUS-4029: Preserve semantic chips in the core composer (#2303)
  Make plugin signature enforcement opt-in (#2212)
  NEXUS-4156: Add workspace Leads and choose a chat's workspace (#2788)
  feat(plugins): report conclusively retired update providers (#3263)
  feat(messages): let attachment renderers open files from the host file card (#2239)
  feat(charts): bundle a Charts code-block renderer (#3226)
  Expose native reply grouping through Conversation.ui (#3245)
  NEXUS-4163: Keep plugin-owned chat deletion in Solo (#2787)
  NEXUS-4156: Expose Solo Workspaces to plugin regions (#2786)
  NEXUS-4022: Start region chats in the New Chat editor (#2784)
  feat(link-previews): unfurl web links below messages by default (#3225)
  fix(messages): keep names in literal Markdown as written when editing (#2834)
  feat(plugins): fetch a packaged managed plugin policy from a URL (#2504)
  fix(goose): enable deferred tool loading for goose agents (#3227)
  fix(unread): preserve manual intent in captured explicit reads (#3228)
  NEXUS-4337: Expose retained plugin update reviews (#3075)
  feat(conversation): add a link preview slot below messages (#3219)
  feat(plugins): let link previews read a public page's preview fields (#3217)
  Let sidebar row plugins decorate ordinary Solo chats (#3222)
  ...

* origin/main: (121 commits)
  Expose Solo region state before a component mounts (#3296)
  fix(builderlab): say a 401 was refused, not expired, and show each sign-in failure once (#3241)
  feat(agents): file new Solo chats in explicit personal workspaces (#2857)
  perf(css): limit broad style invalidation (#3267)
  Delay and fade in the Bestie badge celebration (#3292)
  fix(github): show private-repo body images from signed links (#3252)
  NEXUS-4029: Preserve semantic chips in the core composer (#2303)
  Make plugin signature enforcement opt-in (#2212)
  NEXUS-4156: Add workspace Leads and choose a chat's workspace (#2788)
  feat(plugins): report conclusively retired update providers (#3263)
  feat(messages): let attachment renderers open files from the host file card (#2239)
  feat(charts): bundle a Charts code-block renderer (#3226)
  Expose native reply grouping through Conversation.ui (#3245)
  NEXUS-4163: Keep plugin-owned chat deletion in Solo (#2787)
  NEXUS-4156: Expose Solo Workspaces to plugin regions (#2786)
  NEXUS-4022: Start region chats in the New Chat editor (#2784)
  feat(link-previews): unfurl web links below messages by default (#3225)
  fix(messages): keep names in literal Markdown as written when editing (#2834)
  feat(plugins): fetch a packaged managed plugin policy from a URL (#2504)
  fix(goose): enable deferred tool loading for goose agents (#3227)
  ...

Signed-off-by: Tyler Longwell <[email protected]>
Co-authored-by: Eva <011987e296fd5006292d2f930b574be47c7801048d1983c46c425d3c95f0cffd@buzz.block.builderlab.xyz>

…iews (#3466)

## Problem

Link previews (#3219, #3225) find a message's preview URLs with
`previewLinks`. For any body with an `https://` link, that function
called `prepareMarkdown`, then scanned the prepared content again with
`scanMarkdown`, and kept no result. The renderer already prepares the
same body through its own cache.

A link-bearing row therefore parsed its Markdown two or three more times
than a row without links, on every mount. It did this again on each
remount while scrolling or switching channels.

## Change

- `markdown-preparation.ts`:
- Owns the cache of recent prepared bodies. `recentResults` and
`preparedBodies` move here from `MessageMarkdown.tsx`, unchanged.
  - Exposes it as `preparedMarkdown(content, scanned?)`.
- `prepareMarkdown` takes an optional `scanned` callback that receives
the scan it made. It stays pure and keeps no state.
- `MessageMarkdown.tsx` reads through `preparedMarkdown`, with the same
cache and budget as before.
- `preview-links.ts`:
- Uses `preparedMarkdown`. On a fresh preparation it takes the scan
through the callback instead of scanning again.
- Keeps recent preview link lists in a `recentResults` cache. The key is
the content and exclusions; the weight counts both the key and the URLs.
Cached lists are frozen.
- `preview-links.test.ts` asserts that the renderer and previews
together scan a body once. This fails on the previous code.

## Why behaviour is unchanged

- `prepareMarkdown` is pure, so a cached prepared body is identical to a
fresh one.
- The scan passed to the callback is the scan of the returned `content`,
the same input previews scanned before.
- The link list depends only on content and exclusions, which are both
in the cache key.

## Evidence

Interleaved A/B on 9 Linux and 9 macOS boxes:
- 6 rounds × 2 samples per variant on each box, so n=108 per variant per
OS.
- 4× CPU throttle.
- Values are the mean of per-box medians.

The baseline is `main` (`7bb45482`) with #3464 and #3465 applied. This
change was measured on top of that. The measured revision handed the
scan over through module state instead of a callback; the parse count is
the same. A variant with preview scanning disabled entirely is the
ceiling.

| case | metric | Linux base | Linux PR | Δ | macOS base | macOS PR | Δ
| ceiling Δ (Linux / macOS) |
|---|---|---|---|---|---|---|---|---|
| thread scroll open | script ms | 636.4 | 618.3 | −2.8% | 381.4 | 368.2
| −3.5% | −2.9% / −3.7% |
| | task ms | 997.3 | 976.1 | −2.1% | 600.6 | 588.1 | −2.1% | −1.4% /
−2.0% |
| | LoAF blocking ms | 551.7 | 534.3 | −3.1% | 271.2 | 258.4 | −4.7% |
−2.5% / −5.4% |
| | first rows ms | 937.1 | 914.1 | −2.5% | 561.5 | 546.2 | −2.7% |
−1.8% / −2.7% |
| cold markdown channel open | script ms | 495.6 | 487.8 | −1.6% | 320.6
| 316.8 | −1.2% | −2.0% / −1.7% |
| fast scroll paging (markdown) | LoAF blocking ms | 1489.8 | 1444.2 |
−3.1% | 83.7 | 83.5 | −0.3% | −2.3% / −5.3% |

- Thread scroll open improved on every box (9/9) for script and LoAF on
both OSes.
- The change recovers all the time that link-preview scanning costs in
these scenarios.
- An earlier A/B of desktop-v0.7.18 against the same baseline put thread
scroll open at +2.6% script on both OSes, which this removes.

## Checks

- `vitest run src/features/messages`: 3119 pass.
- `link-previews.spec` and `markdown-documents.spec` pass on chromium
and webkit.
- `bin/pnpm check` is clean.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Signed-off-by: Kalvin Chau <[email protected]>
Co-authored-by: Claude Opus 5.5 <[email protected]>

…lt" (#3480)

Reverts #3225