Add Chronicle-style activity summaries

[haasonsaas]

Summary

• add agentd activity window presets, Markdown output, and local summary-resource writing
• include Chronicle-style provenance, display ids, stale-after metadata, drop accounting, and GitHub PR workstream extraction
• document the new local activity layer and its privacy/source-of-truth boundaries

Test Plan

• swift test
• xcrun swift-format lint --strict --recursive Sources Tests Package.swift
• git diff --check
• python3 scripts/chronicle_parity_audit.py --strict
• smoke-tested agentd activity --window 10m --format markdown and --write-summaries against local batches

[cursor]

PR Summary

Medium Risk
Adds new local summary outputs and file-writing behavior for agentd activity, which could impact privacy/safety if sanitization or redaction is incomplete. Changes are contained to diagnostic/summarization paths and include new tests and explicit consumption guidance.

Overview
Adds Chronicle-style local activity summaries to agentd activity, including window presets (10m/6h/24h), selectable output (json vs markdown), and an optional --write-summaries mode that writes instructions.md plus timestamped resources/*.md files.

Extends ActivitySummary to include provenance and navigation metadata (stale-after timestamp, source batch ids, display ids), GitHub PR workstream extraction from sanitized URLs/metadata, and Markdown rendering that emphasizes the summaries are untrusted navigation aids with drop accounting retained.

Updates CLI help, documentation, and tests to cover the new flags/output, and introduces URLPrivacyRedactor usage in summaries to keep URL query/fragment redaction consistent with other local support surfaces.

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[cursor]

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