fix(slack): enable preview streaming in flat DMs (replyToMode: off) (#76330)

Summary:
- The PR enables Slack draft preview streaming for flat DMs in all non-off modes, updates Slack streaming tests/docs/config metadata/changelog, and refreshes small guard baselines.
- Reproducibility: yes. source-reproducible on current main: the helper returns false for `mode: "partial"` in ...  current test asserts that disabled path. I did not run tests because this review was explicitly read-only.

Automerge notes:
- Ran the ClawSweeper repair loop before final review.
- Included post-review commit in the final squash: fix(slack): enable preview streaming in flat DMs (replyToMode: off)
- Included post-review commit in the final squash: fix(clawsweeper): address review for automerge-openclaw-openclaw-5654…

Validation:
- ClawSweeper review passed for head 52e5d74ef9.
- Required merge gates passed before the squash merge.

Prepared head SHA: 52e5d74ef9
Review: https://github.com/openclaw/openclaw/pull/76330#issuecomment-4365017023

Co-authored-by: clawsweeper <274271284+clawsweeper[bot]@users.noreply.github.com>
Co-authored-by: bob <637186+HangGlidersRule@users.noreply.github.com>

docs/.generated/config-baseline.sha256

@@ -1,4 +1,4 @@
-27444d825e0dda91c769267beb81b3826ca42fd9c2e16d4d6bedccbc5cbccba4  config-baseline.json
+bb58618ecdd5cb16d985eafa4a3a4634f366e6674f3db16c246336e6e02a3706  config-baseline.json
 b95cc4a3b15e688afa58cf700dac425af4e50fd092209e75903e73d5d2988717  config-baseline.core.json
-07005d122bda68081d530ae5cd455ffbc0817f7fb94bd462c4f25edc94a0546c  config-baseline.channel.json
+f2a1aad257c570b497865680c331568a6775369528749826dfa35c1f644483fc  config-baseline.channel.json
 fffe0e74eab92a88c3c57952a70bc932438ce3a7f5f9982688437f2cdaee0bcb  config-baseline.plugin.json

docs/channels/slack.md

@@ -648,8 +648,8 @@ Notes:
 `channels.slack.streaming.nativeTransport` controls Slack native text streaming when `channels.slack.streaming.mode` is `partial` (default: `true`).
 
 - A reply thread must be available for native text streaming and Slack assistant thread status to appear. Thread selection still follows `replyToMode`.
-- Channel and group-chat roots can still use the normal draft preview when native streaming is unavailable.
-- Top-level Slack DMs stay off-thread by default, so they do not show the thread-style preview; use thread replies or `typingReaction` if you want visible progress there.
+- Channel, group-chat, and top-level DM roots can still use the normal draft preview when native streaming is unavailable or no reply thread exists.
+- Top-level Slack DMs stay off-thread by default, so they do not show Slack's thread-style native stream/status preview; OpenClaw posts and edits a draft preview in the DM instead.
 - Media and non-text payloads fall back to normal delivery.
 - Media/error finals cancel pending preview edits; eligible text/block finals flush only when they can edit the preview in place.
 - If streaming fails mid-reply, OpenClaw falls back to normal delivery for remaining payloads.

docs/concepts/streaming.md

@@ -139,7 +139,7 @@ Modes:
 Slack-only:
 
 - `channels.slack.streaming.nativeTransport` toggles Slack native streaming API calls when `channels.slack.streaming.mode="partial"` (default: `true`).
-- Slack native streaming and Slack assistant thread status require a reply thread target; top-level DMs do not show that thread-style preview.
+- Slack native streaming and Slack assistant thread status require a reply thread target. Top-level DMs do not show that thread-style preview, but they can still use Slack draft preview posts and edits.
 
 Legacy key migration:
 
@@ -168,6 +168,7 @@ Slack:
 - `partial` can use Slack native streaming (`chat.startStream`/`append`/`stop`) when available.
 - `block` uses append-style draft previews.
 - `progress` uses status preview text, then final answer.
+- Top-level DMs without a reply thread use draft preview posts and edits instead of Slack native streaming.
 - Native and draft preview streaming suppress block replies for that turn, so a Slack reply is streamed by one delivery path only.
 - Final media/error payloads and progress finals do not create throwaway draft messages; only text/block finals that can edit the preview flush pending draft text.
 

docs/gateway/config-channels.md

@@ -484,7 +484,7 @@ WhatsApp runs through the gateway's web channel (Baileys Web). It starts automat
 
 **Thread session isolation:** `thread.historyScope` is per-thread (default) or shared across channel. `thread.inheritParent` copies parent channel transcript to new threads.
 
-- Slack native streaming plus the Slack assistant-style "is typing..." thread status require a reply thread target. Top-level DMs stay off-thread by default, so they use `typingReaction` or normal delivery instead of the thread-style preview.
+- Slack native streaming plus the Slack assistant-style "is typing..." thread status require a reply thread target. Top-level DMs stay off-thread by default, so they can still stream through Slack draft post-and-edit previews instead of showing the thread-style native stream/status preview.
 - `typingReaction` adds a temporary reaction to the inbound Slack message while a reply is running, then removes it on completion. Use a Slack emoji shortcode such as `"hourglass_flowing_sand"`.
 - `channels.slack.execApprovals`: Slack-native exec approval delivery and approver authorization. Same schema as Discord: `enabled` (`true`/`false`/`"auto"`), `approvers` (Slack user IDs), `agentFilter`, `sessionFilter`, and `target` (`"dm"`, `"channel"`, or `"both"`).