feat(telegram): accept GitHub repo URLs in /linkrepo and /unlinkrepo

[TOMOKI977]

Summary

/linkrepo and /unlinkrepo now accept a pasted GitHub URL as well as owner/repo. Before, pasting a link only returned the usage message.

• New parseRepoReference in src/domain/github.ts reads github.com URLs with or without the scheme or www., with a trailing slash or .git, and with deeper paths such as /pull/17, a query or a fragment. It keeps only owner/repo and then applies the strict validation.
• It rejects other hosts, including lookalikes such as evilgithub.com, and URLs with no repo segment.
• Webhook payload parsing still uses the strict parseRepoFullName, so only chat input gets the lenient form.
• The usage text now says <owner/repo or GitHub repo URL>.

Tests

• New parseRepoReference domain cases, plus a case proving parseRepoFullName still rejects URLs.
• /linkrepo and /unlinkrepo each have a new command test with a pasted URL.
• Full suite: 344/344. tsc --noEmit is clean.

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