feat(practice): per-ring guided hints, Ring-N-of-M progress, and retry mechanic

[TheMeinerLP]

Description

MapDefinition gains optional per-ring hint text to guide players in Practice Mode. The HUD shows ring progress instead of a competitive score bar. Players can retry instantly via teleport and state reset.

Acceptance Criteria

• MapDefinition JSON ring entries accept an optional `hint` string field (e.g. `{"id": 1, "type": "STANDARD", "hint": "Fly through the green ring!"}`)
• Absent `hint` fields are deserialized as `null` / `Optional.empty()` — no validation error
• In Practice Mode, entering a ring with a non-null hint displays the hint as an action bar or title message
• Hint display duration is configurable (default: 3 seconds)
• HUD shows ring progress as `Ring N of M` instead of the competitive score bar in Practice Mode
• A retry action (command or item interaction) teleports the player to the map spawn point
• On retry, all ring-tracker state is reset (rings completed = 0, timer = 0)
• No world reload occurs during retry — pure state reset + teleport
• Gson adapter (`RingEntryAdapter`) handles absent `hint` field gracefully
• Unit tests cover: hint deserialization (present, absent, null), HUD switch, retry state reset

Technical Details

• `hint` is stored in the ring DTO/record (e.g. `RingEntry`); existing entries without `hint` remain valid JSON
• `RingEntryAdapter` lives in `adapter` subpackage, is `final`, follows Gson Adapter naming convention
• `HudComponent` gains a `mode` discriminator or Practice-specific fields (record, compact constructor validates)
• Retry state reset must invoke the same ring-tracker initialization path used at map start

Dependencies

• feat(practice): Practice Mode session — no competitive scoring, repeatable skill drills #172 (Practice Mode session — HUD and retry only activate under `GameMode.PRACTICE`)

Estimate

M