[feat] Add evidence-linked multi-level context answers (#26)

[ThreeLight2000]

Related issue

Fixes #26

Summary

• Extend daily-summary with shared quick, standard, and deep answer variants.
• Preserve Context record IDs and return deterministic source previews.
• Return claim-level support states and remove unsupported source IDs before responding.
• Add Chrome UI controls for answer depth, claim/evidence status, source previews, and record filtering.

AS-IS

flowchart LR
    records[Context records] --> brain[server-brain daily-summary]
    brain --> one[One summary]
    one --> chrome[client-chrome summary view]

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• Current behavior: one summary and key points are returned.
• Problem / limitation: users cannot select explanation depth or inspect which saved records support the answer.

TO-BE

flowchart LR
    records[Context records] --> ledger[Shared source and claim ledger]
    ledger --> variants[Quick / standard / deep variants]
    variants --> chrome[client-chrome summary view]
    ledger --> sources[Source previews and record IDs]
    sources --> library[Existing thought library]

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• Proposed behavior: one evidence basis produces three presentation depths and claim-level support metadata.
• Expected outcome: users see an immediate level-appropriate answer and can inspect or open the supporting record.
• Migration / rollout notes: the existing response remains readable when the new optional fields are absent. No server-context schema or migration is included.

Verification

• pnpm verify
• Package-specific typecheck, test, and build commands

Commands results:

• pnpm --filter server-brain typecheck
• pnpm --filter server-brain test — 22 tests passed
• pnpm --filter server-brain build
• pnpm --filter context-shelf typecheck
• pnpm --filter context-shelf test — 43 tests passed
• pnpm --filter context-shelf build
• pnpm verify — passed

User impact

• Affected clients, servers, packages: apps/client-chrome, apps/server-brain.
• User-visible behavior: Daily Summary now offers answer depth controls, evidence states, source previews, and source-record navigation when Context Server is connected.
• Breaking changes: None.

Metadata checklist

• PR title type and issue number match source branch
• Fixes #26 references the source branch's Issue
• Linked Issue uses the Feature type
• Issue is in the configured Project with its Priority field set — unavailable through the current GitHub integration; limitation is recorded on the Issue
• Mermaid diagrams added for the changed flow

Screenshots recordings

UI changes are confined to the local Chrome extension side panel. No private captures, credentials, tokens, or production configuration are included.