refactor(agent-org): [12/12] replace implementation-phase names with domain terminology

[ShiboSheng]

Dependency and goal

Run only after #840 and after the full eleven-issue Agent Org delivery stack is complete.

Implementation PR numbers are temporary delivery coordinates, not domain terminology. They must not remain in long-lived Agent Org source code, symbols, runtime messages, tests, fixtures, E2E scenarios, or operational comments. This issue owns one final, behavior-preserving naming sweep so future reviewers can understand every name from the code itself without reconstructing the PR stack.

This is a cleanup gate, not a functional debt bucket. Behavioral defects discovered during the sweep stay with their owning issue.

Initial inventory

The current stack already contains examples from PR1–PR4:

• PR1 appears in lifecycle, status, quiescence, and startup comments and in a formal peer-message runtime guidance string.
• PR2 appears in the immutable capability snapshot comment instead of describing the present ownership and consumption boundary.
• PR3 appears in persist_pr3_group_chat_message, its caller, test names, assertions, comments, and a runtime invariant error.
• PR4 appears in Task FSM and recovery comments and errors, pr4_tests.rs, fake-provider constants, functions and markers, fixture IDs, frontend tests, and rendered E2E scenario names.

Future PR5–PR11 findings should be recorded here as they are discovered, then cleaned together only after the stack is complete.

Scope

• Sweep Agent Org production code, tests, fixtures, fake providers, rendered E2E, runtime errors and guidance, logs, comments, constants, functions, module names, filenames, and active Agent Org developer documentation.
• Replace every implementation-phase name with the stable domain concept it represents: lifecycle, quiescence, immutable capability snapshot, typed Turn authority, formal Task FSM, task recovery, pause and resume, archive and delete, writer authority, direct work, group ingress, projection, or compatibility.
• Rename call sites, tests, snapshots, fixture IDs, and E2E selectors and markers consistently.
• Keep user-visible and model-visible messages free of PR numbers and explain the actual rule or corrective action.
• Add a lightweight repository check or documented review gate that prevents new Agent Org identifiers, comments, fixtures, or runtime strings from using implementation PR numbers.

Explicit exclusions

• Architecture and design document sections that intentionally describe the ordered PR 1–11 delivery plan.
• Historical issue bodies, pull-request descriptions, commit messages, handoff records, and audit evidence where the PR number is the subject being documented.
• Unrelated PR-number references outside the Agent Org implementation stack.
• Functional refactors, schema changes, wire changes, persistence-format changes, or test reorganization not required for the rename.

Acceptance

1. Agent Org shipped source contains no PR1–PR11, PR 1–PR 11, pr1_–pr11_, E2E_PR, pre-PR, or equivalent implementation-stage names.
2. Agent Org test names, fixture IDs, fake-provider scenarios, E2E titles, markers, and filenames use stable domain terminology.
3. Runtime errors, tool guidance, logs, and comments state the actual lifecycle or authority rule without referring to a delivery phase.
4. A repository-wide search is reported with an explicit allowlist limited to intentional design and history records.
5. The final report includes an old-name to domain-name mapping so reviewers can verify the sweep.
6. Formatting, compilation, focused Agent Org tests, full agent_core library tests, affected frontend tests, and rendered E2E checks pass.
7. No product behavior, authority boundary, transaction, recovery budget, persistence contract, or rollout behavior changes.

Plain-language contract

A reviewer joining after the Agent Org stack ships should be able to understand every production and test name from the business rule it represents. They must never need to know what PR3 or PR7 happened to contain.