feat(troubleshoot): language-invariant routing signatures + localization lint warning

[dmorosanu]

What

Stacked on #1820. Hardens signature-index routing for clients whose robot hosts run non-English system languages (.NET framework and Office/COM error text localizes with the host language; the index stores canonical English).

Two parts:

1. Invariant signatures for 30 playbooks that previously routed only via localizable message fragments. Every addition is a signal the playbook's body already documents verbatim — exception classes, HTTP statuses, Google/Graph error reason codes, HRESULTs, Healing Agent operation codes/allowance fields — promoted into signatures: with discriminating notes wherever a value is claimed by more than one playbook. No playbook bodies changed; no values invented (files whose bodies document nothing invariant were deliberately left untouched).
2. A lint warning in build-signature-index.py (INVARIANT_KINDS): a signature-bearing playbook with no invariant-kind signature is flagged — warning only, never affects the exit code. Baseline drops 68 → 38 warnings; the remaining 38 are genuinely message-only per body content and stay covered at runtime by SKILL.md's localized-text rule (route on invariant signals first; translate non-English messages to canonical English before grepping — added on refactor(troubleshoot): tiered signature-index investigator (v2 architecture) #1820).

Index regenerated: 215 playbooks, 674 signatures (+43), 22 silent. Manifest-command verifier and index freshness pass.

Language-invariance model

Signature kind	Localizes?
exception, error-code, error-code-prefix, http-status, message-key	Never — class names, codes, statuses, resource keys are language-invariant
message	Host-side messages (.NET, Office/COM) localize; cloud-service messages (Orchestrator API, Graph/AADSTS, IS DAP-*, Slack codes) stay English
state	API enum values are invariant; UI-quoted labels may not be

Validation

The 8 scenarios whose playbooks sit in the affected class (no-host-pending, getasset-network-connectivity, getasset-per-robot-no-value, healing-agent-no-license, python-loadscript-engine-init, o365-createfolder-invalid-path, invokevba-trust-access, plus no-healing-agent whose fixture evidence contains non-English UI text) are running against this branch — results will be posted as a comment.

[dmorosanu]

Validation complete (local, judge-graded, skill loaded from this branch): 8/8 SUCCESS, all at 1.000, single iteration each (one scenario took a second iteration by simulator flow, still 1.000).

Scenario	Score	Wall
no-host-pending	1.000	5.4 min
getasset-network-connectivity	1.000	14.1 min
getasset-per-robot-no-value	1.000	5.2 min
healing-agent-no-license	1.000	7.8 min
python-loadscript-engine-init	1.000	10.7 min
o365-createfolder-invalid-path	1.000	5.2 min
invokevba-trust-access	1.000	6.5 min
no-healing-agent (non-English fixture evidence)	1.000	7.1 min

Selection rationale: these route through playbooks in the message-only (localization-exposed) class that this PR hardens — they are the first to break if the invariant-first prioritization or the added signatures steered routing wrong. No regression; the added signatures coexist with the message routing on English fixtures.