v0.8.69: Distribution channel migration to CodeWhale-native install and update names

[Hmbown]

Related: #3477

Problem

CodeWhale is gaining a website install/update script, but the broader distribution story still contains legacy deepseek-tui surfaces: Homebrew tap/formula names, website install copy, update instructions, legacy npm/package compatibility notes, release assets, and migration docs.

The legacy names should remain compatible where required, but new users should see a CodeWhale-native install/update path first.

Scope

Create a coherent distribution-channel migration plan for CodeWhale-native names.

Audit and align:

• codewhale.net/install.sh and install page copy
• Homebrew tap/formula path and legacy compatibility language
• npm package and old deepseek-tui compatibility guidance
• Cargo/crates install docs
• release asset naming and checksum manifest expectations
• website FAQ/install/guide pages
• update commands shown in docs and UI
• release checklist items that still refer to legacy package names

Non-Goals

• Do not break existing legacy installs.
• Do not imply DeepSeek model/provider support is deprecated.
• Do not publish, tag, or rename external distribution channels without maintainer approval.

Acceptance Criteria

• The primary website install path uses CodeWhale-native naming.
• Legacy deepseek-tui paths are clearly marked as compatibility paths.
• Homebrew strategy is documented: rename, alias, or compatibility-only, with rollout steps.
• Release checklist clearly states which assets/packages are canonical and which are legacy.
• Update docs do not send new users toward legacy names unless that channel is intentionally still legacy-only.
• Add website install/update script at codewhale.net/install.sh #3477's install.sh work fits into this channel plan.