[Repo Assist] refactor: use result.Parameters in DeepLinkHandler instead of re-parsing query

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🤖 This is an automated draft PR from Repo Assist.

Summary

DeepLinkParser.ParseDeepLink already parses the query string into result.Parameters (a case-insensitive Dictionary(string, string)). The Handle method was then calling DeepLinkParser.GetQueryParam on the raw query string a second time for the send and agent cases — redundant work that re-implemented parsing logic that had already run.

Change

• Replace GetQueryParam(query, "message") with result.Parameters.GetValueOrDefault("message") in the send and agent switch cases
• Remove the now-unused query local variable (previously var query = result.Query)

No behaviour change — both approaches produce identical results because ParseDeepLink uses Uri.UnescapeDataString and case-insensitive key comparison, same as GetQueryParam.

Why this is better

Before	After
Query string parsed twice (once in ParseDeepLink, once in GetQueryParam)	Parsed once; already-available data is reused
Two code paths that must stay in sync	Single parse site
query variable held but passed to a static re-parser	result.Parameters used directly

Test Status

503 tests passed (18 skipped — Windows-only integration tests), 93 Tray tests passed. No failures introduced.

Passed!  - Failed: 0, Passed: 503, Skipped: 18, Total: 521
Passed!  - Failed: 0, Passed: 93,  Skipped: 0,  Total: 93

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