fix(agents): decode camelCase API responses, draft the suggested action

[liamcervante]

Why

preview_fix has been returning 500 {"error":"failed to generate action config"} for FinOps tagging findings. Reproduced on the demo org:

$ infracost tasks preview-fix 5f352453-… --finding-id 3491a601-… --org appleaccount
Info: generating action: Agents API returned status 500: {"error":"failed to generate action config"}

Root cause is a wire-contract drift in our Agents client. The API serializes its domain types straight to JSON (c.json<FindingDetail>(finding)), and the Agents API renamed those types from snake_case. Our structs still declared snake_case tags, so every multi-word response field silently decoded to its zero value. Single-word fields (id, title, status, effort) kept working, which is why nothing looked obviously broken. Before this change:

$ infracost findings get a09a7a2c-… --json
"finding_id": "",  "event_type": "",  "occurred_at": ""
# and estimatedMonthlySavings / suggestedAction / actionDescription / createdAt absent entirely

That's how we get to the 500. Agents deliberately downgrades a tagging fix to create_ticket when the resources aren't Terraform-managed (taggingPrEligibility.ts), but suggestedAction never reached the caller — so preview-fix fell back to its hardcoded open_pr, and generate-action 500s for a task with no repo to name.

Anything added to the API since June has never worked in the CLI.

What changed

Wire contract

• Retagged Finding / Task / Action / FindingEvent / FindingTaskEvent to camelCase. Request bodies moved too (taskIds, actionType, dismissedReason) — Agents dual-accepts both casings today, and its own comments call our snake_case a compat shim, so this is the safe window to migrate off it.
• Response fields that are genuinely snake_case server-side stay put, with a comment saying why: action_id, and the report endpoint's learning_id / dismissed_action_ids / confirmed_action_ids, are hand-built route literals rather than serialized domain types, so #515 never touched them.
• Dropped has_running_actions / integration_id (no server counterpart at all); added lifecycleState / remediationState / prUrl (part of the current contract).

Paging — findings list is offset-paginated (page / per_page → {items, pagination}), so --cursor was a silent no-op pinning every caller to page one. Now --page, and the result carries page / total_findings / total_pages / next_page.

Action type — preview-fix now defaults to the task's own suggestedAction. Explicit --type still wins and skips the lookup; a failed lookup or a task with no suggestion falls back to open_pr; a manual suggestion errors with what to do instead. The --type flag defaulted to "open_pr" at the cobra layer, which would have defeated this. MCP tool descriptions updated to tell the agent to omit type.

One extra fix in the same path — create-fix discarded the {type, config} envelope's type and defaulted to open_pr, so piping a ticket draft straight through submitted it as a PR. It now honors the drafted type unless --type is given. This only started to matter once tagging tasks actually drafted tickets.

Verified against the live API

findings get   → orgId, agentName, taskTotal, lifecycleState, createdAt, triggerDetail,
                 suggestedAction: "create_ticket"        (all previously "")
findings list  → "Saving: $143.00/mo"                    (previously absent)
                 "Showing 3 of 16 findings — pass --page 2 to see the next page."
preview-fix    → 422 {"code":"not_connected","error":"Connect a project management
   (the 500)      integration to create tickets."}
preview-fix    → open_pr, repo_url https://github.com/infracost-demo/data-warehouse
   (PR-eligible tagging task — unchanged)

A TestClientGetFindingDecodesCamelCaseFields case pins the wire casing against a payload shaped like coast's FindingDetail, so this can't rot silently again.