Trim Build iOS plugin prompts

[dimillian-oai]

Summary

• normalize the Build iOS Apps plugin starter prompt to the current plugin prompt-array contract
• shorten the plugin-level prompt on both metadata surfaces so it stays under the starter-prompt budget
• tighten all eight Build iOS skill trigger descriptions while preserving routing terms such as App Intents, ETTrace, memgraphs, XcodeBuildMCP, Liquid Glass, and Observation

Why

Build iOS Apps was tripping prompt-length warnings in Codex. Its manifest starter prompt was also a string while the current plugin surface expects starter prompts as an array capped at three entries and 128 characters per entry.

The skill descriptions were still large enough for plugin-eval to fail the plugin trigger-cost budget after the starter prompt fix, so this PR keeps the trigger metadata compact without moving any skill behavior out of the skill bodies.

Impact

The plugin keeps the same skill inventory and workflows, but its discovery text is smaller and the starter prompt is a short Simulator-oriented prompt.

plugin-eval report progression

The same local report command was used throughout:

cd plugins/plugin-eval
node ./scripts/plugin-eval.js analyze ../build-ios-apps --format markdown

Before the manifest prompt was normalized, plugin-eval could not emit a scored report because the string-shaped defaultPrompt hit:

((intermediate value) || []).join is not a function

State	Score	Risk	Checks	Trigger	Invoke	Deferred	Active	Total
First scored report after starter-prompt normalization	59 / D	high	1 fail, 6 warn, 2 info	754	11829	37211	12583	49794
After explicit Use when trigger wording	68 / D	high	1 fail, 4 warn, 2 info	753	11829	37212	12582	49794
Final after compacting all Build iOS skill descriptions	77 / C	medium	0 fail, 5 warn, 2 info	354	11431	37212	11785	48997

The final report clears the failing trigger-cost check. Remaining warnings are static budget warnings for trigger/invoke/deferred text plus existing Python helper complexity and missing Python tests.

Validation

• node ./scripts/plugin-eval.js analyze ../build-ios-apps --format markdown
• git diff --check