tech-debt(ci): code-quality.yml attributes 4133+1281 pre-existing mypy errors to closed #7105 #15345

What

code-quality.yml's two informational mypy steps, and the strict autobot_shared
check's suggested suppression syntax, all cite GH#7105 as the tracker for their
pre-existing error counts:

• code-quality.yml:500 — "Errors in the backends are tracked in GH#7105."
• code-quality.yml:503 — suggests # type: ignore[code] # GH#7105 for new suppressions
• code-quality.yml:510 — "4133 pre-existing errors tracked for resolution in GH#7105" (autobot-backend/, informational)
• code-quality.yml:515 — "1281 SQLAlchemy Column[T] errors tracked in GH#7105" (autobot-slm-backend/, informational)

#7105 is CLOSED ("ci: mypy is installed but never invoked — silent-tuple bug
from #7078 would have been caught"). It tracked making mypy run at all, not
resolving what running it found. Once it closed, mypy started running and
surfaced 4133 + 1281 pre-existing errors — but nothing was filed to track
those, so the workflow kept citing the issue that was actually done.

Found while fixing #15333 AC3, which flagged this exact citation as stale.

Why this matters

A reader hitting the GH#7105 reference today finds a closed issue and
reasonably concludes the backlog is either resolved or being tracked
elsewhere. Neither is true — the two steps are still (informational) /
non-blocking, and the counts in the comments (4133, 1281) are whatever was
true when someone last hand-updated them, not a live measurement.

Scope

This issue is the tracking placeholder the workflow comments should cite
instead of #7105. It does not itself fix the underlying mypy errors — that
is 4133 + 1281 individual findings, almost certainly wrong to batch into one
ticket. Whoever picks this up should:

• Re-measure the current error counts for autobot-backend/ and
  autobot-slm-backend/ (the numbers in the workflow comments are unverified
  as of this filing).
• Decide whether the backlog should be broken into per-package or
  per-error-code follow-up issues, or resolved as one sustained effort.
• Update or retire the code-quality.yml comments once a decision is made,
  the same way #15333 retired the #7105 citation.

Acceptance criteria

• Current mypy error counts for autobot-backend/ and autobot-slm-backend/ are re-measured and recorded here
• A concrete plan (single effort vs. decomposed) is chosen and recorded
• code-quality.yml's suppression comments cite whichever issue(s) actually track the resolution work