Issue #3620617: Documentation that describes code which no longer exists

Corrects the documentation claims in the issue that are no longer true, one commit per finding.

Verified against the source and fixed (23 findings):

• the assignment plugin ids are users_variable and roles_variable; there are four staffing audiences, not three, and no plugin with id variable
• the flow-condition diagnostic method is summary(), so an override named explain() would override nothing
• the example_quorum ballots all use the structured assignments form; none uses the flat modeler fields
• four config examples used a script task type and one a task type; neither exists
• the kernel ships seven task-type primitives (variables and user_operation were missing)
• advancement is synchronous by default; the queue is the other execution mode
• Resume is one of the five recovery actions on the instance page, not an API-only operation
• the engine method that brings a retry forward is retryToken()
• Views exposes five Orchestra entities; the orchestra_incident base table was undocumented
• the durable audit log ships as orchestra_audit_trail; it is not a future step
• the variable audit event is off by default, and record_variable_values was undocumented, which made two safety claims on the page untrue
• the inbox access check is checkActionAccess(), not actAccess()
• the interaction reference tables named InteractionController::step, signalOutcomes and ParkNotificationDispatcher, none of which exist, and omitted two routes
• the handler_url migration section documents a mechanism with zero occurrences in the codebase, so it is dropped
• entity_form is an interaction plugin, not a task type, and the follow-ups the content README plans both ship
• the kernel plugin-type list was missing VariableProvider and DeadlineProvider; the submodule table was missing four modules
• subprocesses now have their own page and nav entry, documenting all seven config keys
• the notification event carries tokenData, and its attachments are read through getProcessInstanceAttachments()
• timers are in the kernel, not a submodule
• the cards library and the status palette are in orchestra_presentation
• the requester permission is titled View own Orchestra process instances
• the interaction-chains page contradicted itself on the token field (chain, not chain_id) and on the milestone flag (stacking.keep, not sticky); its per-issue build log is dropped
• an instance pins no version under the Off mode or after pruning, not because it predates the feature
• the examples table listed 5 of the 11 shipped example workflows

Found stale, no change needed: both OpenAPI findings were already corrected on 1.x by #3620616. The document names drive orchestra api on all three write operations, documents 403 everywhere and documents the three set-variable limits.

Deferred, as the issue asks: the README Status / docs/extending.md compatibility contradiction is a stage decision for the beta-preparation issue, not a documentation error.

Also fixed in passing: a stale human-tasks.md#pull-based-operations-no-inbox-record anchor in the roadmap.

phpcs, phpstan, cspell (from the mirror root, over the changed files, with the project dictionary subtracted) and the per-project translations check are all green.

This merge request was prepared with the assistance of an AI agent (Claude). The changes and the wording were reviewed by me before pushing, and accountability for the content is mine.