Why This Matters

Six modules independently define a private _truncate() function with inconsistent implementations, different ellipsis characters, and undocumented magic limits. Adding a new delivery channel or integration means writing yet another truncation function from scratch.

This is the same class of duplication fixed in #869 for the GitLab write-back flow.

Current State

discord_delivery.py and telegram_delivery.py use the Unicode ellipsis …; everything else uses "...". mariadb.py also has a second ad-hoc truncation at line 294 using "\n... (truncated)".

Proposed Fix

1. Add app/utils/truncation.py with one shared helper:

def truncate(text: str, limit: int, ellipsis: str = "...") -> str:
    if len(text) <= limit:
        return text
    return text[: limit - len(ellipsis)] + ellipsis

2. Migrate all six call sites to use it.
3. Keep each module's limit constant where it is — only the function body moves.

Tests / Coverage

• one parametrised test: text under limit → unchanged, text over limit → truncated with correct ellipsis
• one test for Unicode ellipsis variant
• existing tests for all six modules must stay green

Acceptance Criteria

• _truncate is defined in exactly one place
• ellipsis character is consistent or explicitly configurable per call site
• no behaviour change for any existing caller
• scope limited to the six files listed above