docs(ci): align sync resolver/fixer/analyzer prompts with wiring-aware reasoning

[mateo-di]

Summary

Aligns the upstream-sync automation prompts with the reasoning that actually found and fixed the v1.92.0 regressions. That sync shipped three CARTO features which passed every automated check yet were functionally broken, and two of the prompts' own heuristics caused the loss. This is the prompt/doc half of the long-term hardening (Workplan B); the mechanical test-reaction wiring is #125 (Workplan A), which this is stacked on.

The three failure classes, none catchable by "does the pattern still grep":

1. Dropped call site across an auto-merged file — streaming_iterator.py (conflicted) lost a param while handler.py (auto-merged) kept passing it → TypeError on every streaming request.
2. Orphaned helper — _patch_get_session_from_redis survived byte-for-byte but its caller was replaced by upstream's → sessions written to Redis, read from the batch-delayed DB → multi-turn context loss.
3. Cross-version data-format drift — upstream began b64-encoding response ids; CARTO's unchanged store keyed Redis by the encoded id while lookup used the decoded id → 100% session-lookup miss.

Changes

Resolver prompt (carto-upstream-sync-resolver.yml):

• Verbatim-first rule (restore CARTO blocks byte-identical from carto/main, diff-verified; adapt only where an upstream API change forces it, minimal + # CARTO PATCH). Replaces "preserve the BEHAVIOR, not necessarily the exact file versions".
• Removes the harmful heuristics: "bigger file = probably correct" deleted; "upstream TAG code WORKS" reframed as "works for upstream's call graph, not necessarily CARTO's".
• Adds three post-resolution checks: orphan sweep, cross-file wiring (auto-merged siblings), cross-version data-flow.
• References the regression canaries as the definition of "wired correctly".

Fixer prompt (carto-upstream-sync-ci-fixer.yml):

• Same verbatim-first rule + orphan sweep + call-graph reframing.
• Manifest-aware loop guard: the "3+ fixes → sync entire file from upstream" escape hatch now excludes manifest files (blind sync is how wirings get erased).

Analyzer prompt (carto-upstream-sync-customizations-analyzer.yml):

• Judge PRESERVED_CARTO by WIRING, not string presence: an orphan / missing call site / broken data-flow is INCORRECTLY_DROPPED even when the pattern greps OK. It had reported the dead session read as PASS ✅.

Docs (CARTO_UPSTREAM_SYNC.md): new troubleshooting section with the three wiring-loss classes and detection commands.

Ordering / dependencies

• Stacked on fix(ci): restore agent reaction to test failures via CARTO Feature Tests #125 (Workplan A) — base will auto-retarget to carto/main when fix(ci): restore agent reaction to test failures via CARTO Feature Tests #125 merges. Both ultimately target carto/main.
• Overlaps fix(ci): gate carto/main PRs on CARTO feature tests and harden the sync resolver #124 on the resolver prompt (both harden it); if fix(ci): gate carto/main PRs on CARTO feature tests and harden the sync resolver #124 merges first, the cross-file-wiring prose dedups trivially.
• Deferred to a follow-up (task tracked): enriching carto-features.yml with call-site/wiring patterns so the blocking manifest check catches orphans by grep too. Left out here because the open v1.92.0 sync PR rewrites that manifest and editing it now would conflict.

Test plan

• All three workflows parse as YAML; 73 run: blocks pass bash -n
• No prose references stale/removed heuristics
• Acceptance (manual, post-merge): replay the pre-resolution state of a sync against the updated resolver prompt and confirm it produces the wiring fixes (or fails loudly) without human intervention