docs(skills): shorten and front-load the skill descriptions

[JonMUnity]

For this PR, I tried to shorten the skill descriptions to make the plugin more performant for Codex.

This branch was created from the branch used to create this PR: #74.

Here is a table comparing the character limit changes. "Before" is what's on main now and "After" is the current branch.

Skill	Before	After
generate-editor-search-query	1009	214
setup-vivox-voice-chat	968	207
levelplay-unity-integration	967	271
implement-in-app-purchases	927	282
optimize-text-mesh-pro	698	224
ui	666	204
unity-cli	647	286
build-live-game	641	246
physics-3d-collision	640	232
new-unity-project	604	201
tilemap-ruletile-createfromsegment	592	208
migrate-birp-to-urp	550	198
unity-package-management	536	241
manage-sprite-atlas	528	187
setup-multiplayer-services	499	218
ui-imgui	495	183
optimize-audio	418	241
audio-setup-mixers	417	222
optimize-web	394	207
initialize-ai-navigation	394	200
tilemap-ruletile-createempty	383	213
sprite-segment-3x3grid	348	196
localization	339	203
sprite-editor	294	157
validate-urp-render-graph-renderer-feature	283	200
ui-uitk	264	200
urp-postprocessing	238	178
ui-ugui	213	186
tilemap-palette-create	211	148
shader-graph-create-custom-node	171	159
2d-pixel-perfect	133	220
Total	15,467	6,532

[jthorborg]

Audio LGTM regardless, but could be more aggressively trimmed.

Having authored some of these original skills and seeing the description evolved, I'm curious as to why we made those changes in the first place, or if we can somehow measure agent performance impact of doing this.

[leoyaikUnity]

Sprite Editor skill LGTM

[JonMUnity]

Audio LGTM regardless, but could be more aggressively trimmed.

I'm going to try and trim all of them a bit more aggressively, since we're still far from where want to be.

Having authored some of these original skills and seeing the description evolved, I'm curious as to why we made those changes in the first place, or if we can somehow measure agent performance impact of doing this.

These changes are being done primarily to satisfy a requirement from Codex. Codex will drop skills at a point when character limits exceed a threshhold. Apart from that, we're broadly trying to work towards aligning skill descriptions to our rules here: https://internal.docs.unity.com/en-us/docs-quality/documentation/skill-model. This guidance was written mostly as a synthesis over Anthropic's guidance, so the field is a bit muddied now with these requirements from Codex.

[JonMUnity]

Apologies to my reviewers. I made even more judicious reductions to try and fit Codex requirements.

[karljj1]

Approving skills/localization/SKILL.md

[Antoine-Lassauzay]

Approved on behalf of the UI team, but I agree there is a subtle change of meaning to the UI routing skill that may lead agents to bypass it.

[leoyaikUnity]

Approve for 2D

[JonMUnity]

Approved on behalf of the UI team, but I agree there is a subtle change of meaning to the UI routing skill that may lead agents to bypass it.

@Antoine-Lassauzay I changed the description for the routing table in response to yours and @ziyiunity's feedback.