feat(labels): an unknown --label names the team's real labels (PHNX-4105)

[muqsitnawaz]

feature. The warning an agent sees when it passes a label that does not exist now tells it what to use instead.

Tracking: https://linear.app/getrush/issue/PHNX-4105

What changed

• linear — _unknown_label_message(label, names) next to _suggest: label 'x' not found, skipping. plus a did-you-mean for a near miss, then Labels are owner-managed: pick one of the team's N (sorted, first 12, …); full list: linear labels. Both call sites use it: _build_create_input (create) via warn, and the update --label path via its Warning: print. No behavior change beyond the message: the label is still skipped, the create or update still proceeds. Nothing new is denied.
• test_linear.py — UnknownLabelMessageTests: full-list text, did-you-mean, elision at 12, and the create path printing the hint while still building the input.
• CHANGELOG.md — Unreleased entry.

Verification

Screenshot of the real run: python3 -m unittest (224 OK, 4 skipped) and two linear update PHNX-4105 --label … calls against the live team on my own closed ticket, where the update path prints the new warning with the team's 25 labels and, for bugs, Did you mean: Bug?. No label was added.

🤖 Generated with Claude Code

https://claude.ai/code/session_01FQ3w5SAvum8nShzmBo21Ar

[muqsitnawaz]

APPROVE — independent non-author review (code-reviewer subagent, session 87d560af, reviewed at 3768c4c; suite run on the PR head, 224 OK). Both call sites still skip the label and proceed, names come from the unfiltered team list, output is stderr only, bulk create is unaffected (verbose=False never prints), sorted() is safe because IssueLabel.name is a non-null String, tests cover the helper and the create path, only linear/test_linear.py/CHANGELOG.md changed, no version bump. One SHOULD (empty-team wording read "team's 0 ()" and the count lacked its noun) applied in 552a087 with a test; suite 225 OK, 4 skipped.