feat(fitbit): compose health Content and Wake context

[kachofugetsu09]

Summary

• replace Fitbit proactive registrations and proactive-only MCP tools with an ordinary Core Timer plus content.source.v1 adapter
• keep the monitor as the single Fitbit cloud poller, submit durable health items to Content, and keep sleep as overwriteable current context
• append fresh sleep context only to channel=wake without aborting, replacing prompts, or changing passive turns
• preserve candidate/formal isolation and recover ACK after process interruption
• rotate diagnostic monitor.runtime.log at 1 MiB with three retained generations while leaving health, Content, and Session ledgers untouched

Fact ownership

• Content settled items retain the complete health payload and settlement history
• monitor pending/acked data remains the monitor current queue projection
• sleep_context is an overwriteable current snapshot
• Session remains append-only
• diagnostic logs are bounded and rotated

Validation

• Python: 56 passed against Core 9da3a988a2bf62b0f550bd4f6bb98c4eeb1f56f5
• Node: 12 passed
• targeted Pyright: 0 errors
• compileall and Plugin API v3 contract passed
• real manager candidate/formal interaction passed
• independent runtime-log subprocess fixtures: 7 passed
• exact head a7ba644 received independent Terra xhigh APPROVE
• git diff --check and worktree status clean

Recovery

Pre-change bundle: /mnt/data/coding/backups/fitbit-content-context-20260823/pre-migration-eda9a879.bundle
Additional pre-fix bundles record both Terra repair stages.

This PR does not deploy or change the formal hua-home workspace.