fix: repair duplicate topic map wiring during template push

[max-braintrust]

Stack 2/3: duplicate topic map repair. Base: inline code facets (#410) (max/observability-inline-code-facets). Next: scoped automation settings (#409).

Older template pushes could attach a new map even when the facet already had one under a different slug. A later push then fails because the facet has multiple attached topic maps.

With --force, keep the oldest attached map, breaking timestamp ties by function ID, and detach the duplicates from Topics automations. This keeps the retained map's customization and reports. Detached maps stay in the project; human and JSON push output list them. Other facet and map references stay attached.

Checks: 19 active_observability tests passed, including repair of duplicate wiring while retaining the original map's customization and reporting the detached map. Cargo formatting and README Prettier passed. Clippy passed with the existing large_enum_variant warning in the root command enum suppressed.

[github-actions]

Latest downloadable build artifacts for this PR commit b3261bb9fe2e:

• Workflow run: https://github.com/braintrustdata/bt/actions/runs/37853111815
• Download all artifacts (GitHub CLI): gh run download 37853111815 --repo braintrustdata/bt
• Installers are published from main automatically. To publish one for a PR branch, run release-canary manually via workflow_dispatch.

Available artifact names

• artifacts-build-local-aarch64-pc-windows-msvc
• artifacts-plan-dist-manifest
• artifacts-build-global
• artifacts-build-local-aarch64-unknown-linux-gnu
• artifacts-build-local-x86_64-apple-darwin
• artifacts-build-local-x86_64-pc-windows-msvc
• cargo-dist-cache
• artifacts-build-local-x86_64-unknown-linux-gnu
• artifacts-build-local-x86_64-unknown-linux-musl
• artifacts-build-local-aarch64-apple-darwin