What Problem This Solves

Supersedes #95522 with a clean branch rebuilt on top of the latest main.

#95522 conflicted after #95183 landed on main. Latest main already contains the default progress placeholder / delayed-clear fixes from #95183, so this PR intentionally keeps only the remaining assistant-preview/config/SDK/docs changes.

This fixes the remaining Telegram progress-streaming gap where a short assistant preview could not share the same progress fallback lane cleanly. The PR:

• adds the Telegram progress assistantPreview lane
• scopes assistantPreview to streaming.mode = "progress"
• bounds the initial preview delay
• updates Telegram config hints and generated config metadata
• updates plugin SDK streaming surface coverage
• adds regression coverage for progress, partial, block, and off streaming modes

Evidence

Clean Branch / Conflict Resolution

This branch was rebuilt from the current origin/main and replays only the commits that are still unique to the assistant-preview feature. It avoids reintroducing the #95183 placeholder changes that are already merged into main.

Current head: 732094f75f900bdf914d290ed41336e7a46ecdf2

Commits over latest main:

• feat(telegram): add progress assistant preview lane
• fix(telegram): scope assistant preview config
• test(telegram): align assistant preview with rich progress drafts
• test(plugin-sdk): account for assistant preview public surface
• fix(telegram): bound assistant preview initial delay
• fix(plugin-sdk): gate assistant preview to progress mode

Real Behavior Proof

Dedicated Telegram test bot proof from the corrected late segment of the original recording:

• GIF: https://raw.githubusercontent.com/snowzlmbot/openclaw/ad7e8c792476817dab2a56f789bb2125c5f0f40f/evidence/pr-95522/telegram-proof-core.gif
• MP4: https://raw.githubusercontent.com/snowzlmbot/openclaw/ad7e8c792476817dab2a56f789bb2125c5f0f40f/evidence/pr-95522/telegram-proof-core.mp4
• Checksums: https://raw.githubusercontent.com/snowzlmbot/openclaw/ad7e8c792476817dab2a56f789bb2125c5f0f40f/evidence/pr-95522/SHA256SUMS.txt

The clip shows:

• progress placeholder appears first
• short assistant preview appears through the assistant-preview lane
• final answer replaces the preview path
• progress draft cleanup still happens correctly

Local Targeted Validation

git diff --check origin/main...HEAD
node scripts/plugin-sdk-surface-report.mjs --check
pnpm config:channels:check
pnpm config:schema:check
node scripts/run-vitest.mjs \
  test/scripts/plugin-sdk-surface-report.test.ts \
  src/plugin-sdk/channel-streaming.test.ts \
  src/agents/model-runtime-policy.test.ts \
  extensions/telegram/src/bot-message-dispatch.test.ts \
  extensions/telegram/src/draft-stream.test.ts \
  extensions/telegram/src/lane-delivery.test.ts \
  src/channels/progress-draft-compositor.test.ts

Result: all listed checks passed; targeted Vitest passed 282 tests total.

Risk

Low-to-medium. The feature is scoped to Telegram progress streaming and explicitly gated so assistantPreview only affects streaming.mode = "progress". Regression tests cover the non-progress modes to prevent preview leakage into partial, block, or off.