docs(develop-app): workflow-first analysis pattern + clearer layer z-order

[srtena]

Two improvements to the carto-develop-app skill.

1. Complex analysis → Workflow, called from the app

Previously workflows-and-sql.md framed a workflow as just "one of two ways to run SQL" and led with ad-hoc query(). The skill is now explicit that non-trivial analysis belongs in a workflow, not inlined as app SQL:

• New decision rule at the top of workflows-and-sql.md (with a why: one source of truth, public-token apps leak SQL to the browser, perf) plus a situation → action table.
• Two app-side call paths documented accurately: read the output table (static/scheduled) vs. CALL the compiled procedure via the Workflows API (on-demand/parameterized).
• Agent path: a new "Workflow as an MCP tool" section — when an embedded agent drives the analysis, publish the workflow as an MCP tool rather than handing it raw SQL.
• Corrected a factual error: the old text guessed the procedure name as wf_<workflow_id>; it's a hash-based FQN in the connection's workspace dataset. Doc now says get it from carto workflows mcp describe, and notes the token must grant the procedure and the tables it reads.
• Surfaced as an always-on bullet in SKILL.md so it's reached at decision time.

2. Clearer layer z-order — anchored on the layers themselves

The real confusion is the deck.gl layers array, not the basemap:

• Rewrote the "Layer order" section in layers.md: z-order is the array (last = top); CSS z-index does nothing to layer stacking; rebuild the array, don't mutate it; "won't restack" is usually a stale array reference. Plus polygonOffset / depthCompare: 'always' (v9 spelling — old depthTest: false is gone) and the 3D depth-test caveat.
• Replaced the basemap-and-view.md "out of scope for v1" punt with the validated overlaid-vs-interleaved fix: a *_NOLABELS basemap, or MapboxOverlay + interleaved: true + beforeId: 'watername_ocean'.
• Added an always-on z-order bullet to SKILL.md.

Validation of the z-order facts (done against primary sources, not asserted)

• Fetched the live CARTO Positron style JSON: 93 layers; watername_ocean (index 67) is the first label layer, so it's the right beforeId to slip fills under all labels; waterway_label (index 13) is a trap that sits below roads. Same IDs across Positron / Dark Matter / Voyager.
• Confirmed against deck.gl's official MapLibre docs that beforeId: 'watername_ocean' is the exact value their own example uses, and that interleaved requires maplibre-gl@>3 (WebGL2).

Notes

• No new files, no catalog.json change → make sync not required.
• make validate passes (validate_skills: OK (23 skills), validate_snippets: OK (520 snippets)).

🤖 Generated with Claude Code