### Summary

Reported by @awayspam in #77260: in v2026.5.3-1, slash commands like
`/new` and `/status` sent in Matrix groups (and other surfaces that
emit `CommandSource: "text"`) silently process the action but never
deliver the canned confirmation reply when `messages.groupChat.visibleReplies`
is set to `"message_tool"`. Worked in v2026.4.25.

`resolveSourceReplyDeliveryMode` exempts `CommandSource === "native"`
from the `message_tool_only` suppression so Slack/Mattermost slash-menu
replies stay visible. Matrix and Tlon set `CommandSource: "text"` for
every inbound message, so the bypass never triggers — the canned
command reply gets routed through `message_tool_only`, no message tool
runs, and the user never sees feedback even though the action ran.

### Fix

Replace the `CommandSource === "native"` exemption inside
`source-reply-delivery-mode.ts` and `dispatch-from-config.ts`'s
`prefersMessageToolDelivery` calculation with a shared
`isCommandSourceTurn(ctx)` predicate:

- `CommandSource === "native"` → exempt (unchanged behavior for
  Slack/Mattermost slash-menu replies).
- `CommandSource === "text"` AND the body starts with `/` → exempt.
  Matrix and Tlon set `CommandSource: "text"` for every inbound, so the
  body-starts-with-`/` requirement keeps normal user prose under the
  configured visibility policy while still letting the slash command
  reply through.
- Otherwise → no exemption.

`isCommandMessage(ctx.CommandBody ?? ctx.Body ?? "")` reuses the existing
`commands-registry.ts` predicate to detect slash-prefix bodies, so the
exemption matches the same set of inputs that `runCommands` will execute.

### Tests

`src/auto-reply/reply/source-reply-delivery-mode.test.ts` adds:

- `isCommandSourceTurn` describe block: 4 cases proving the predicate is
  true for native (any body), true for text + `/`-prefix, false for
  text + non-slash body, and false for empty/missing CommandSource.
- `resolveSourceReplyDeliveryMode`: a regression case for the exact
  reported scenario (Matrix `/new` with `visibleReplies: "message_tool"`),
  a counter-case proving non-command Matrix/Tlon prose stays under
  `message_tool_only`, and a CommandBody-fallback-to-Body case.
- `resolveSourceReplyVisibilityPolicy`: regression case mirroring the
  reporter's scenario at the policy layer (suppressDelivery → false,
  deliverySuppressionReason → ""), and a counter-case for prose under
  `visibleReplies = "message_tool"` (suppressDelivery still true).

All 26 tests in the file pass; 101 tests in the adjacent
`dispatch-from-config.test.ts` pass after the predicate is wired into
`prefersMessageToolDelivery`.

### Reproduction

1. `messages.groupChat.visibleReplies: "message_tool"` in `openclaw.json`.
2. Send `/new` in a Matrix group.
3. Before this PR: action runs (session resets, command logged), no
   visible reply in the channel.
4. After this PR: canned `"✅ New session started."` reply lands in
   the channel.

Native (Slack/Mattermost slash-menu) command replies and normal user
prose on Matrix/Tlon are unchanged.

### Verification

- `pnpm test src/auto-reply/reply/source-reply-delivery-mode.test.ts src/auto-reply/reply/dispatch-from-config.test.ts src/auto-reply/reply/get-reply-inline-actions.skip-when-config-empty.test.ts` → 141/141 pass (clawsweeper acceptance criteria).
- `pnpm test:changed` → 6416/6416 pass (one unrelated import-only suite failure on `web-tree-sitter` — pre-existing local env issue).
- `pnpm exec oxfmt --check --threads=1 src/auto-reply/reply/source-reply-delivery-mode.ts src/auto-reply/reply/source-reply-delivery-mode.test.ts src/auto-reply/reply/dispatch-from-config.ts` → clean.

Fixes #77260.