fix: recover display-name telegram authors

[igorrendulic]

Summary

Telegram support can now recover evidence for users whose visible author identity is stored as a display name rather than author_username. A draft-context --user crinx7 style lookup no longer falls through to missing_user_history when the local Telegram message is linked to users.display_name, and indexed chunks now render the visible author label instead of unknown.

This also cleans up noisy Telegram chunk text by dropping blank neighbor messages, and adds rebuildable language/translation helper metadata so English helper context can aid search without replacing the original Telegram text. Agent-facing instructions now treat target.language as the reply-language signal and keep translated_text as operator/helper context only.

Design Notes

• Display-name matching is an exact fallback only when author_username is absent, so arbitrary text mentions are not promoted into author matches.
• Original Telegram text remains the evidence source of truth; translated text is indexed and returned only as helper metadata.
• draft-context prefers the target message language over neighboring context when drafting from a message ID.

Validation

• uv run pytest -> 136 passed
• git diff --check -> clean
• Code review applied one fix: mixed-language message windows now prefer the target message language before surrounding thread language.

Known Residuals

• Language inference is still intentionally lightweight. Latin-script non-English messages may be classified as English until a real language detector or stricter confidence policy is added.
• Exact author lookup is correct but not yet optimized for large profiles; a normalized author key or index-backed lookup would reduce scan risk.

Post-Deploy Monitoring & Validation

• Validation window: first local profile re-index after release.
• Owner: support operator running the local profile.
• Commands to validate:
  • scripts/tg-support --profile default index
  • scripts/tg-support --profile default search crinx7
  • scripts/tg-support --profile default draft-context --user crinx7
  • scripts/tg-support --profile default draft-context --message-id <known-non-English-message-id>
• Healthy signals: display-name-only users appear with their visible author label, missing_user_history is absent for known display-name histories, blank author: lines do not appear in evidence text, and non-English target contexts include target.language when inferred.
• Failure signals: search returns unrelated low-score results for known display-name authors, draft context reports missing_user_history for visible display-name users, or replies are guided by translated helper text rather than target language.
• Mitigation: re-run sync and index; if the issue persists, fall back to draft-context --message-id and disable reliance on target.language until language detection is tightened.

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