fix(permissions): keep colons in argument values from truncating patterns

[parveshsaini]

Closes #3766

What

parsePattern split a permission pattern on every :, so any argument value
containing a colon was truncated. A deny rule written against a URL —
fetch:url=https://evil.com/* — parsed as url = "https", which never matches a
real URL, so the rule silently never fired (fail-open). Windows drive paths
(shell:cwd=C:\work\* → C) were corrupted the same way.

This parses the tool name up to the first :key= argument condition, then takes
each value up to the next :key= boundary rather than the next colon, so
colons inside a value are preserved. Tool names with colons
(mcp:github:create_issue) are unaffected — they were already handled by
splitting at the first :key=, and that behaviour is unchanged.

Why

This is the sibling of #3605. That fix made matchGlob's wildcards cross
path separators, but with a colon in the value the pattern never reaches
matchGlob intact — so the same fail-open direction was still reachable for URLs
and Windows paths, which are exactly the kind of value an operator writes a
deny rule against. In non-interactive / auto-approval runs, or alongside an
overlapping allow, a corrupted deny is a real bypass. allow rules with
colon values were broken too, but those fail closed.

Tests

Added to pkg/permissions/permissions_test.go:

• TestParsePattern rows for URL, Windows-drive, and mixed value-colon +
  second-condition patterns.
• TestDenyRuleWithColonInValue — end-to-end via CheckWithArgs: a deny rule
  with a URL value now returns Deny, plus a shell-command-with-URL case and a
  colon-free control.

Each new assertion fails against main and passes with this change; the existing
TestParsePattern rows (including mcp:github:create_issue) are untouched.

Verification (in golang:1.26.5 + golangci-lint:v2.12.2, matching CI)

$ go test ./pkg/permissions/...
ok  	github.com/docker/docker-agent/pkg/permissions

$ golangci-lint run ./pkg/permissions/...
0 issues.

$ gofmt -l pkg/permissions/    # (no output)

Confirming the tests are meaningful — reverting only permissions.go to main
while keeping the new tests:

--- FAIL: TestParsePattern/fetch:url=https://example.com/*
        expected: map[string]string{"url":"https://example.com/*"}
        actual  : map[string]string{"url":"https"}
--- FAIL: TestParsePattern/shell:cwd=C:\work\*
        expected: map[string]string{"cwd":"C:\\work\\*"}
        actual  : map[string]string{"cwd":"C"}
--- FAIL: TestDenyRuleWithColonInValue
        expected: 2 (Deny)   actual: 0 (Ask)
        Messages: deny rule with a URL value must block the matching URL

---

[Sayt-0]

looks good to me !