feat(chatarchive): add --format flag for machine-readable output (JSON)

[CodeMonkeyCybersecurity]

Problem

The archive result is currently only emitted via structured logging (otelzap). For scripting and CI integration, operators need machine-readable output without parsing log lines.

Proposed fix

Add --format flag with values: text (default, current behavior) and json (outputs Result struct as JSON to stdout).

eos create chat-archive --format json | jq '.unique_files'

References

• Eos CLI patterns: human-centric output with machine-readable escape hatch
• Similar to kubectl get -o json, gh issue list --json

Acceptance criteria

• --format json outputs valid JSON Result struct to stdout
• --format text (default) behaves identically to current behavior
• E2E smoke test for JSON output parsing

[CodeMonkeyCybersecurity]

SOAPIER session note (2026-03-20)

Objective assessment

• Reviewed internal/chatarchivecmd/run.go. Current CLI behavior writes a human-readable summary to stdout and structured fields to logs, but there is no machine-readable result mode yet.

Analysis

• This is a clean follow-up from the chatarchive hardening branch, with no overlap beyond shared code paths in internal/chatarchivecmd and the pkg/chatarchive.Result shape.

Related

• Sibling follow-ups: feat(chatarchive): add file locking or flock for concurrent archive runs #91, feat(chatarchive): add incremental archive with file modification time tracking #93, chore(chatarchive): add golangci-lint configuration for chatarchive package #94.