[Bug]: Goal-issue progress comment never posts — journal issue_number is never set

[chronoai-shining]

Summary

The rolling per-run progress comment on the goal issue never posts: the journal record's issue_number is initialized to None and is never set to a real goal-issue number in any production path, so the activity-comment upsert always early-returns — the goal issue shows only lifecycle labels, never progress.

Scope Check

• This bug is within fkst-hosted scope — user-facing run observability on the goal issue.

Affected Area

• Backend (Rust)
• Frontend (React)

Environment

• Branch / commit: develop (verified on feat/144-config-observ-deploy)
• Deployment: any

Steps to Reproduce

1. Set FKST_JOURNAL_ACTIVITY_COMMENT_ENABLED=true (the default) with journaling configured.
2. Trigger a goal and watch the goal issue during the run.

Expected Behavior

A rolling activity comment on the goal issue reflects RAISED-event progress as the run proceeds (the behavior #139 set out to provide).

Actual Behavior

upsert_activity_comment early-returns "no issue_number; skipping activity comment" on every flush because issue_number is never populated:

• issue_number is initialized None (fkst-journal lib.rs:208).
• It is only ever re-hydrated from the already-committed journal file (flush.rs:124-125) and propagated if already set (merge.rs:98-99).
• No production code path sets it to the real goal-issue number (grep: the only setters are the self-hydration + tests).

Net: the goal issue receives lifecycle labels only (fkst-running / fkst-completed / …); the durable progress lives solely in the separate journal repo's .fkst-hosted/journal/<run_key>.json. The advertised "rolling issue comment" surface does not exist.

Affected Files

• fkst-journal crate: lib.rs (~208), flush.rs (~124-125, ~370-376), merge.rs (~98-99).
• The session driver that constructs the journal context (fkst-control-plane/src/sessions/service.rs start_journaler; worker engine/journal.rs) — where the real goal-issue number would be threaded in.

Proposed Resolution

Thread the goal issue's number into the journal SessionCtx/record at run start so upsert_activity_comment can post/maintain the rolling comment — OR, if the comment surface is intentionally dropped, default FKST_JOURNAL_ACTIVITY_COMMENT_ENABLED=false and remove the dead seam + docs claiming an issue comment.

Verification Checklist

• With the feature enabled, a live run produces and updates a single activity comment on the goal issue.
• A test asserts issue_number is populated from the real goal issue (not only self-hydrated).

Definition of Done

Either the rolling goal-issue progress comment works end to end, or the dead seam is removed and documentation/config defaults corrected. Relates to #139.