Deploy and observability guidance give contradictory infrastructure ordering

## Baseline

`5a306f8956cb1eeae69f9709de0e4d61b44e11e7` (v1.3.1)

## Reproduction

1. Check out the baseline commit.
2. Compare the deployment workflow in `skills/google-agents-cli-deploy/SKILL.md` with the Agent Runtime order in `skills/google-agents-cli-observability/SKILL.md`.
3. Also inspect the README and Starter Pack migration entry points for an authoritative ordering rule.

## Actual behavior

The deploy skill says not to run `infra single-project` before deployment and describes it as optional. The observability skill says Agent Runtime users must run it before the first deploy. README and the migration guide do not resolve the target/ownership distinction. A user following different entry points can therefore receive opposite instructions.

Issue #2 reports a related downstream symptom: applying Terraform after an imperative Agent Runtime deployment can create or target a second Runtime. This issue tracks the separate documentation root cause across the four user entry points.

## Expected behavior

All four entry points should use one decision table:

- Basic Agent Runtime / Cloud Run: deploy directly.
- GKE: deploy performs the required targeted Terraform.
- Terraform-managed observability, any target: run `agents-cli infra single-project --apply` before deploy.
- Existing imperative deployment: do not apply Terraform afterward without importing or deleting before switching; otherwise keep imperative ownership and configure observability manually.

## Minimal fix

Add the same compact decision table to README, the migration guide, deploy skill, and observability skill; remove the conflicting statements; add a text contract test that requires the table and rejects the old contradictory wording.

Tested fix:

- Fork branch: https://github.com/benagentai93-dot/agents-cli/tree/codex/batch-5-doc-skill-consistency
- Root-cause commit: https://github.com/benagentai93-dot/agents-cli/commit/d68dcdf

## Verification

- Documentation contract tests: **7 passed**
- Full test suite: **99 passed**
- `ruff check src tests`: **passed**
- `ty check src`: **passed**
- `uv build`: **passed**
- Built wheel installed normally; `agents-cli --version` returned `1.3.1` on Python 3.11 and 3.13

I am not opening a PR because the upstream repository currently does not accept PRs.