feat(identity): rebrand deferred extension, mobile, MCP, and distribution surfaces

[absolutepraya]

Goal

Complete the Marka identity work that was intentionally deferred from the public repository/domain cutover. This issue covers visible distribution surfaces and their public-facing copy without changing compatibility-sensitive package, protocol, or persisted-data identifiers by accident.

Scope

• Rebrand browser-extension visible name, descriptions, context menus, logos, and UI copy.
• Rebrand mobile visible app names, labels, and assets while preserving bundle IDs and deep-link schemes unless a separately approved migration covers them.
• Rebrand MCP README, visible descriptions, installation guidance, and distribution copy.
• Rebrand CLI and shared-skill user-facing copy while preserving package scopes, executable compatibility aliases, and KARAKEEP_* variables.
• Audit npm, SDK, app-store, extension-store, and MCP distribution metadata for coupling to obsolete public repository, hostname, or GHCR values.
• Update only coupling that would break because the Marka repository/domain/package moved. Do not rename package scopes, export formats, protocol keys, bundle IDs, extension IDs, or persisted paths without a dedicated compatibility plan.

Non-goals

• Landing site publication remains feat(landing): establish a fork-owned Marka landing site #25.
• Hosted documentation publication remains docs: publish fork-owned Marka documentation at docs.marka.abhipraya.dev #26.
• Broad internal identifier renaming remains intentionally not planned unless a concrete compatibility problem justifies a focused issue.
• Do not rewrite historical records or upstream-owned distribution identities merely to remove the Karakeep name.

Acceptance criteria

• Browser extension user-visible identity consistently presents Marka.
• Mobile user-visible identity consistently presents Marka without breaking existing installed-app links.
• MCP and CLI-facing documentation presents Marka and points at current resources.
• Shared agent skill presents Marka while the compatible CLI/env contract remains usable.
• npm, SDK, app-store, extension-store, and MCP metadata has been audited for broken coupling.
• Any retained compatibility identifiers are documented with a reason.
• Focused tests/builds/checks pass for each changed distribution surface.

[absolutepraya]

Audit 2026-08-22: valid, but partially satisfied. The source browser-extension manifest and mobile app display name already present Marka, while compatibility identifiers such as KARAKEEP variables, bundle IDs, and schemes should remain unless separately migrated. The remaining gap is visible distribution copy and metadata: apps/mcp/README.md:24-52 still uses Karakeep server labels and an upstream GHCR image, and packages/sdk/README.md:1-3 and :41-48 still presents the SDK as Karakeep with upstream documentation. Keep the issue open, narrow the remaining work to unsatisfied distribution surfaces, and document retained compatibility identifiers. Severity:medium reflects a public identity and installation guidance gap, not a core runtime outage.