Close-or-rewrite #843–#861 after the #834 stack merges #934

What

All 19 sub-issues of #834 — #843 through #861 — are still open, and all 19 are superseded by the definition-layer stack (#880 → #882 → #883 → #897 → #898 → #899 → #900 → #901 → #902).

The PRs originally opened against them, #863–#877, were closed unmerged when the epic was restructured from one-PR-per-sub-issue into the current stack. So the issues have no live PR, and the work most of them describe has been done differently.

Why this needs a pass rather than a bulk close

The stack merges as one unit and its layers carry no Fixes #<n> trailers for these numbers, so nothing closes them automatically. But they are not uniformly obsolete either — they fall into three groups, and the third is the reason this is a task and not a script:

1. Fully delivered by the stack. The per-workflow path definitions (e.g. the missing self-paths in CI paths: Python Lint — add self-trigger path #843–CI paths: TS Typecheck — add self-trigger path and tsconfig.build.json #846). Close as completed, referencing the layer that delivered each.
2. Superseded in approach. Sub-issues describing a one-workflow-at-a-time migration that the stack did wholesale. Close as not planned, with a pointer to the stack.
3. Still live, but re-homed. Anything whose substance survived into CI paths: dirsql-checks ci-paths — assert workflow filters and Mergify anchors agree #862 (the ci-paths check) or into the post-Epic — CI: run only the checks relevant to the changed paths #834 docs pass. These should be closed only after confirming the requirement is actually captured in the successor issue — otherwise the epic silently drops a requirement.

Walk all 19, sort them into the three groups, and close each with the appropriate state_reason and a one-line pointer. Rewrite rather than close where the substance survives and has no home yet.

Sequencing

Do this after the stack merges, not before — the "delivered by" pointers need real merge commits, and closing early would make the epic look finished while it is still in flight.

Then

Once #843–#861 are resolved and #862 lands, #834 itself can close.