hermes - 💡(How to fix) Fix feat(gateway): cross-topic session fork — branch a Telegram session into a different topic

Problem

Telegram's topic/thread system maps naturally to Hermes session isolation — each topic = one session. Currently /branch (or /fork) creates a fork within the same topic, which means you can't have two independent continuations of the same session in separate topics.

Use Case

A user has a long-running session in Topic A. They want to branch it into Topic B to pursue a sub-task or alternative direction, while keeping the original conversation alive in Topic A. Both branches should share the parent context but evolve independently.

Real-world example:

• Topic A: "AdaptProbe development" (main session)
• User types /branch --topic <topic-b-id>
• Topic B: "AdaptProbe — WebUI experiments" (forked session, starts with full context from A)

Desired Behavior

A way to fork the current session into a different Telegram topic, either via:

Option A: Flags on /branch

/branch --topic <topic-id>
/branch --new-topic

Option B: New slash command

/fork-to <topic-id>

Both approaches would:

1. Clone the current session's context (history, memory, skills)
2. Create a new session bound to the target topic
3. Leave the original session untouched in the source topic

Current Workaround

Manual export + paste context into new topic. Clunky and loses session metadata.

Why This Matters

For users who use Telegram topics as their primary session management interface, cross-topic forking is the natural equivalent of "open in new tab" — it unlocks parallel exploration without losing state.