feat(argocd-wait-sync-multi): emit previousRevision per app

[JesperTerkelsen]

What

Adds a previousRevision field to each entry of the deployments output, so downstream changelogs can show a per-system revert target ("what was live before this deploy") — the thing you reach for during an incident.

Output schema is now:

[{ "name", "app", "revision", "previousRevision", "start", "end", "status", "url" }]

How

previousRevision is extracted from the app's own .status.history — the most recent history revision that differs from the revision we just verified (a "last distinct" filter, so a same-SHA re-sync doesn't report itself as its own previous). It honours the same source-repo source-index selection as revision, since multi-source history entries mirror .status.sync.revisions[] ordering.

• No extra API calls — reuses the app JSON the state machine already fetches each poll.
• Timing-robust — captured the first time we lock onto our revision, and the "differs from verified" filter is correct whether or not ArgoCD has appended the new history entry yet.
• Empty on a first-ever deploy (no prior distinct revision).

Why this shape

Sourced from ArgoCD sync history rather than a git diff so it reflects what ArgoCD actually had synced before, not what a manifests PR intended — that's the accurate revert target.

Verified

bash test/run-tests.sh — green (5/5). Test A now asserts the multi-source app with history reports previousRevision = the prior revisions[0], and the app with no history reports previousRevision: "".

Follow-up

Consumed by changelog-cli (DeployedSystem.previousRevision → a grey "Containers (N)" card rendering previous → new with a compare link per system).

[JesperTerkelsen]

Closing: superseded by a different source for the previous version. We're reading the previous image tag straight from monorepo-typescript-manifests at bump time (consistent with how the single-service deploy already does it via component-deploy.yml), rather than from ArgoCD sync history. The manifests read yields the app image tag (the version humans read + a real code compare link), whereas .status.history gives the manifests commit SHA. Keeping argocd-wait-sync-multi a pure rollout-verifier (timing/status/url); the version identity is joined in downstream.