Copilot PR summary diffhunk links are frequently broken by bad formatting

[Euan-McVie]

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Bug

Copilot Feature Area

Copilot in GitHub

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When using co-pilot to generate a PR summary it frequently generates badly formatted diffhunk links.
This results in them not rendering as links and so requires tedious manual intervention to fix them all.
It appears that the root cause is that it doesn't understand how backticks escape the link formatting.

e.g. It frequently produces:

(`[[1]](diffhunk://#diff-123456789123456789123456789123456789123456789L140-R171)`,
 `[[2]](diffhunk://#diff-123456789123456789123456789123456789123456789R215-R239)`,
 `[[3]](diffhunk://#diff-123456789123456789123456789123456789123456789R292-R298)`,
 `[[4]](diffhunk://#diff-123456789123456789123456789123456789123456789L7-L35)`,
 `[[5]](diffhunk://#diff-123456789123456789123456789123456789123456789L7-R91)`)

resulting in:

([[1]](diffhunk://#diff-123456789123456789123456789123456789123456789L140-R171), [[2]](diffhunk://#diff-123456789123456789123456789123456789123456789R215-R239), [[3]](diffhunk://#diff-123456789123456789123456789123456789123456789R292-R298), [[4]](diffhunk://#diff-123456789123456789123456789123456789123456789L7-L35), [[5]](diffhunk://#diff-123456789123456789123456789123456789123456789L7-R91))

instead of the corrected:

([`[1]`](diffhunk://#diff-123456789123456789123456789123456789123456789L140-R171),
[`[2]`](diffhunk://#diff-123456789123456789123456789123456789123456789R215-R239),
[`[3]`](diffhunk://#diff-123456789123456789123456789123456789123456789R292-R298),
[`[4]`](diffhunk://#diff-123456789123456789123456789123456789123456789L7-L35),
[`[5]`](diffhunk://#diff-123456789123456789123456789123456789123456789L7-R91))

resulting in
([1], [2], [3], [4], [5])

Note that I am not even sure the backticks are required at all so frequently just remove them completely instead of moving them around.

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