Replace telegram_actions log with hash-chained immutable audit trail

[kai-linux]

Goal

Replace the current best-effort runtime/telegram_actions/ action records with a hash-chained, append-only audit log so trust posture is verifiable. Today an attacker (or a buggy hook) could silently mutate or delete an approval record without detection.

Success Criteria

• New orchestrator/audit_log.py exposing append_audit_event(cfg, event_type, payload) that writes to runtime/audit/audit.jsonl with each line carrying {ts, event_type, payload, prev_hash, hash} where hash = sha256(prev_hash + canonical_json(payload))
• All state-mutating events route through append_audit_event: Telegram approvals, kill-switch toggles, mode changes, autonomous issue creation (groomer / log_analyzer), autonomous PR opens, autonomous PR merges
• New audit_verify CLI entrypoint walks the chain and reports any tampering (broken hash link)
• Daily digest gains a "audit chain status: OK" line; on tamper detection, send Telegram alert
• Regression test: synthetic chain validates clean; mutated middle line fails verification; truncated tail fails verification

Constraints

• Audit writes must be atomic (tempfile + os.replace) to prevent partial writes from breaking the chain
• File rotates at 10 MB; rotation preserves the chain across files via a manifest of (file, last_hash)
• Keep the hash function dependency-free (hashlib.sha256 from stdlib)

Task Type

architecture

Why

The audit story today is "tail the log". Telegram approvals, kill-switch flips, and autonomous issue creation all happen via plain JSONL writes that could be silently edited. An immutable chain is the minimum bar before agent-os can claim a defensible trust posture for anything beyond the operator's own machine.

Re-queued Context

• Original issue: Replace telegram_actions log with hash-chained immutable audit trail #247
• Escalated task: task-20260421-121034-replace-telegram-actions-log-with-hash-chained-imm

Last agent summary

Rendered prompt is 133453 bytes, exceeding the 100000-byte ceiling.

Blockers

• Prompt size 133453 bytes exceeds 100000-byte limit.
• Retrying with more prior-attempt context will not help; the task body itself must be trimmed.

Files changed

• None