feat: add sloctl edit command - #460

Adds edit command scenarios for unchanged files, successful edits, editor failures, and invalid identity changes.
Documents e2e fixture generation and debugging conventions.

Use SHELL when launching the editor and document editor and shell fallback behavior in the edit command help.

Preserve validation failures in the edit buffer so users can correct and retry.
Treat reverted edits as canceled and show cleaner API validation messages.

Reject multiple agent names before editing and after object lookup to enforce
the single-Agent constraint and keep the command help text consistent.

Reuse object selection flags and query building across get and edit so edit supports labels, services, and budget adjustment SLO filters.
Handle report and budget adjustment identities without project scoping to avoid edit lookup issues.

Reuse annotation selection parsing for both get and edit so edit annotations can
filter by slo, time range, and category consistently with get behavior.

replace project-scoped type assertions with `v1alpha.GenericObject` access so edit validation works with the parser's generic object model. also add agent and development docs to capture the object-model caveat and repository workflow expectations.

Adapt project scoping checks to the updated `nobl9-go` APIs and use
`v1alpha.GenericObject` only for objects whose kind is project-scoped.
Also make edit selection mismatch errors clearer for project-scoped resources.

Route annotation lookups through `GetCmd` so `get` and `edit` share the same code path.
Build annotation queries explicitly for the `/annotations` endpoint to preserve selection filters.

Convert annotation API responses into typed annotation objects before printing or editing.
Include the project field in annotation selection so filtered edit/get commands target the expected review notes.