v0.8.45 agents: standardize sub-agent naming around whale species

[Hmbown]

Context

The current sub-agent display can still look like raw agent IDs such as agent_55b34f75. For v0.8.45, all sub-agent types should use the same naming source and present friendly whale-species names consistently across the TUI, logs, summaries, and any agent/work panels.

Scope

• Introduce one canonical whale-name registry or naming helper for every sub-agent/session type.
• Use whale species names as the friendly naming pool.
• Include a source note for the species list and clarify the taxonomy boundary: baleen whales, toothed whales, and whether dolphins/porpoises are included as Cetacea or intentionally excluded from the user-facing whale pool.
• Keep names deterministic for a given agent/session ID where possible.
• Handle collisions cleanly once multiple agents are active.
• Keep the raw short ID available in details/logs for debugging.

Acceptance criteria

• Every sub-agent type uses the same naming helper instead of separate ad hoc labels.
• Active agents display friendly whale names instead of only raw agent_* IDs.
• The whale-species list is broad enough for concurrent agents and has a short source/taxonomy note in code or docs.
• Duplicate names are avoided until the naming pool is exhausted.
• Raw IDs remain available in debug/details views.
• Tests cover deterministic naming, collision handling, and fallback behavior.
• cargo fmt --all and relevant agent/TUI tests pass.

[Hmbown]

Related naming split: #2026 should not replace this issue. #2016 is about friendly names for agent instances. #2026 is about route/tier names for model + reasoning effort, ordered by whale size so users can understand depth/cost/speed. They should share a source-backed whale taxonomy but remain separate surfaces.

[Hmbown]

Status update from #2035 (merged as d22da53): deterministic whale-species nicknames are now assigned from stable agent IDs, duplicate names get suffixes, the popup shows friendly names while preserving raw IDs, and the sub-agent tests passed locally plus in CI.\n\nLeaving this issue open for the final acceptance pass across every sub-agent/session surface, logs, summaries, and docs/source-note wording before closing it.

[Hmbown]

Closing as completed in PR #2035 (feat(file): cancellable list_dir with timeout).

Evidence:

• WHALE_NICKNAMES constant with 50+ whale species names (Blue, 蓝鲸, Beluga, Narwhal, Orca, etc.)
• whale_nickname_for_id() for deterministic assignment from agent IDs
• whale_nickname_for_index() for sequential overflow (e.g., "Blue 2")
• SubAgentSnapshot.nickname field exposed in the TUI
• SpawnRequest.nickname field accepted as input
• Tests in crates/tui/src/tools/subagent/tests.rs

The TUI now shows human-readable whale-species names in the sidebar while preserving the raw agent ID in the detail popup.