The Copilot backend relies on the AI to reproduce the footer text exactly,
which leads to subtle differences (URL parameter order, whitespace, emoji
encoding) compared to the git-cliff template in cliff.toml.
Fix: define CANONICAL_FOOTER as a single bash constant and pipe all three
backends (copilot, git-cliff, manual) through ensure_canonical_footer(),
which strips any existing BMAC footer block and appends the canonical one.
Also tell the AI not to generate a footer at all, since it is now added
programmatically. The manual backend gains a footer it previously lacked.
User-Impact: none
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