[REQ-135][CODE] Reject new community Excel installs; keep Alpha Excel only #1012

Covers

Parent AC1–AC2, AC4–AC6 of jinjunnn/alpha-work#65 (REQ-135). Depends on the alpha-web catalog release that drops mcp:excel from the recommended surface (refresh the offline snapshot from that release; do not hand-author alpha-catalog.json).

Portfolio has no tenants: do not keep a legacy community Excel install. Uninstall the durable leaf and receipt; delete the EXCEL_FILES_PATH / excelWorkspaceRoot policy. No compatibility shim.

Boundary

• packages/ui-mac/src/shared/office-advisories.ts — add mcp:excel / excel-mcp-server to the bundled office-retire table (deny install). Do not relabel it as alpha-excel.
• packages/ui-mac/src/main/ext-advisory-gate.ts and Hub — new installs fail.
• Boot or install-path teardown: remove mcp.excel-mcp-server from durable config and its global receipt so Hub no longer lists it.
• packages/ui-mac/src/main/ext-mcp-policy.ts — delete excelWorkspaceRoot / applyExcelWorkspacePolicy / EXCEL_FILES_PATH injection from the write policy. Tests assert the path is gone.
• packages/ui-mac/src/renderer/extensions/alpha-catalog.test.ts and planner/policy/seed tests that currently require mcp:excel on the recommended surface.
• Factory skill office-docs: community excel is not an install option.
• docs/design/req-135-retire-community-excel.md plus a surgical amendment of docs/design/req-133-office-four-format-hub.md (coexistence sentence superseded).
• Offline catalog snapshot refresh after the web release. CHANGELOG Unreleased if Hub copy changes.

Out of scope

• Signing / publishing the web catalog (sibling CODE).
• Copying files out of ~/Alpha/excel-workspace into the current project.
• REQ-134 {workspace} spawn substitution.
• Whole-disk grants.
• Changing archived Word/PPT keep-installed behavior.

Exit condition

Merged PR + bin/check green + documentation impact handled.
No runtime capture, screenshots, or security acceptance here.

Parent

Refs jinjunnn/alpha-work#65 (native sub-issue; never a closing keyword against the parent)