feat(client): show character details in rich presence

[zoeyrose]

Closes #171

Summary

• Add an explicit Server, zone and character Rich Presence tier.
• Share the active character name and level only while playing and only at the new tier.
• Preserve existing tiers, elapsed session time, redaction, normalization, coalescing, and rate limits.
• Update client documentation, setting text, and the affected player-view settings digests.

Coordinates

• Base: main at 69fad049c939894a3bb18755db078ed0d21da611
• Head: feat/client/discord-character-presence at 0f373d53fff09aee881db134479818f25c7b8745
• Worktree: workspace/worktrees/classic/issue-171

Validation

• Focused client-rich-presence CTest: pass.
• Reconnect/session replacement regression coverage: pass within the focused test.
• python3 tools/verify_import_history.py: pass.
• git diff --check: pass.
• ./atrinik build client --profile issue-171 --test: build and 35/36 tests pass locally. The unrelated live client-face-stream test cannot initialize its ephemeral QUIC listener in this environment; CI must confirm that expected check.

Manual verification

For an opt-in live smoke test, use a developer-owned Discord application ID and a running Discord desktop client with the issue-owned issue-171 Classic-derived profile. Select Server, zone and character, enter play, and verify <character name> - Level <level>, friendly server/zone, and stable elapsed time. Change level, downgrade privacy, disconnect/reconnect, and switch characters; verify no stale character data. Direct servers must show Private server only. Shut down only the exact test topology with ./atrinik down NAME; do not apply cleanup while this PR is open.

[codecov]

Codecov Report

❌ Patch coverage is 58.33333% with 25 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
client/src/client/rich_presence_policy.c	61.40%	12 Missing and 10 partials ⚠️
client/src/client/rich_presence.c	0.00%	3 Missing ⚠️

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