feat(chat): show the player head before the prefix in chat

[TheMeinerLP]

Summary

• Chat lines formatted by Butterfly now start with the sender's player head (object component), then a space, the prefix and name, : and the message, on Paper and Minestom.
• The head carries the skin textures from the Paper profile / Minestom Player#getSkin(); without textures it is sent with UUID and name only. Names Adventure rejects as head names (e.g. Bedrock names with spaces) are omitted so chat never fails.
• New setting butterfly.chat.head.enabled (default true), added to both bundled default-config.yaml files; invalid values fall back to the default with a warning.
• Display name, tab list name and team prefix are unchanged. The head is built once per message and composed through the new pure ChatLine/PlayerHeads helpers in api.

OpenSpec

• Archives replace-togglz-with-avaje-config and restrict-chat-tags-by-permission.
• Adds add-player-head-to-chat.
• Records the manual Paper test results of the two archived changes.

Tests

• PlayerHeadsTest (5), ChatLineTest (4), 3 new ButterflySettingsTest cases, Minestom chat/head/config tests; 143 tests in api and minestom in total.
• ./gradlew build :minestom:smokeTest green.

Manual test

Paper 26.2, LuckPerms 5.5.71, ViaVersion/ViaBackwards 5.12.1, 26.2 client (build of 509a1fa):

• config.yaml created on first start with all defaults (incl. chat.head.enabled), unchanged on second start (identical sha256).
• Legacy flags.properties in the server root: one warning, ignored.
• sort-format "%02d" gives team 01default; key removed with -Dbutterfly.format=%03d gives 001default; default gives 0001default.
• Tags: without permissions <red>rot <click:run_command:/help>klick</click> stays literal; after lp group default permission set butterfly.chat.tag.color true the text is red and the <click> tag stays literal.
• Head: shown before the [Test] prefix with the player's skin; with butterfly.chat.head.enabled: false there is no head and no leading space.

Before merge

• Check the chat line with a client older than 1.21.9 via ViaBackwards and record what it shows.

https://claude.ai/code/session_01Wt7kcAoVtZTEALDSX4CxWF

[github-actions]

Test results

 38 files   38 suites   25s ⏱️
150 tests 150 ✅ 0 💤 0 ❌
300 runs  300 ✅ 0 💤 0 ❌

Results for commit e789b66.