fix(emlx): preserve and expose RFC Message-ID

[salmonumbrella]

What changed

• Preserve RFC Message-ID during raw email import and repair missing IDs when re-importing Apple Mail archives.
• Link replies to a unique parent in the same source, including parents imported later and interrupted imports.
• Expose rfc822_message_id in analytics SQL and show-message --json, including daemon connections. Rebuild caches with the added column.

Why

Apple Mail imports kept Message-ID in raw MIME but left the stored identifier empty. That prevented SQL queries and JSON clients from using it to identify messages or construct Mail.app links.

Usage

Re-import the same directory and source identifier to fill missing IDs, then rebuild the cache:

msgvault import-emlx --no-resume me@example.com ~/Mail/INBOX.mbox/
msgvault build-cache --full-rebuild
msgvault show-message 123 --json
msgvault query "SELECT id, rfc822_message_id FROM messages LIMIT 10"

New and repaired IDs use the original case without angle brackets. Existing nonempty IDs stay unchanged. Wrap and URL-encode the ID for a Mail.app link, such as message://%3CCase-ID%40example.test%3E.

Closes #815

[roborev-ci]

roborev: Combined Review (4621830)

Verdict: Changes require fixes for 1 finding.

Medium

• internal/mime/message_id.go:31-37: ParseMessageIDs passes the entire In-Reply-To header to a single-ID normalizer, so RFC-valid values with comments or multiple message IDs normalize to empty and cannot be linked. Parse In-Reply-To as a message-ID list, ignoring comments and folding whitespace, resolve valid candidates using the unique-parent rule, and add coverage for comments and multiple IDs.

  Reported by: codex

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Reviewers: 2 done | Synthesis: codex, 7s | Total: 14m46s

[wesm]

looking

[roborev-ci]

roborev: Combined Review (e065aa8)

Verdict: Changes require fixes for 2 findings.

High

• internal/store/email_headers.go:115-120: The reply-page query uses ? placeholders directly with PostgreSQL, which requires $1, $2, etc.; EMLX imports will fail during reply resolution. Run the query through s.Rebind(...) or a store query wrapper, and add PostgreSQL coverage for the resolver.

  Reported by: codex

Medium

• internal/importer/ingest.go:145-150; internal/store/messages.go:1150: The generic message upsert unconditionally assigns excluded.rfc822_message_id, so upserting an existing message can clear or replace a previously nonempty identifier instead of preserving it. Make the conflict assignment fill-only: retain the stored nonempty ID and use the incoming value only when the stored value is NULL or empty.

  Reported by: codex

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Reviewers: 2 done | Synthesis: codex, 8s | Total: 10m5s

[roborev-ci]

roborev: Combined Review (7f49463)

No issues found.

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Reviewers: 2 done | Synthesis: codex | Total: 10m28s