Make Aspire base port configurable to support parallel stacks across git worktrees

[tjementum]

Summary & Motivation

Centralize the local-development port allocation behind a single source of truth (.workspace/port.txt) and propagate the base port through every layer that previously hardcoded 9000 and friends. Two motivations: enable running multiple Aspire stacks simultaneously from separate git worktrees (each stack on its own non-overlapping port range, with isolated Docker volumes), and remove the scattered hardcoded ports that drifted out of sync across rsbuild configs, test fixtures, the gateway, and the AppHost.

• Add PortAllocation in the shared kernel as the canonical source for the base port. Self-bootstraps .workspace/port.txt to 9000 on first read and computes derived offsets for Aspire dashboard, Postgres, Azurite, gateway, per-SCS API/static/workers, OTel, and MCP
• Accept an optional positional basePort argument on pp run / pp restart and the corresponding MCP tools; written atomically to .workspace/port.txt before any code path lazily loads PortAllocation
• Suffix Docker volume names with the base port for non-default stacks (e.g., platform-platform-11000-postgres-data) so parallel Azurite and Postgres containers do not corrupt each other's state
• Allow pp run and pp restart to operate in a fresh worktree (no port.txt) without false-positive collision warnings against another worktree's running stack
• Switch the Aspire MCP server from HTTP transport (hardcoded localhost:9007) to stdio transport via the Aspire CLI so the integration works on any base port. The README prerequisites now include Aspire CLI install steps for Windows, macOS, and Linux
• Warn when the locally installed Aspire CLI version does not match the Aspire.AppHost.Sdk pinned in AppHost.csproj
• Inject the blob storage connection string from Aspire (renaming the endpoint to blob-storage) so SCS clients honor the dynamic Azurite port instead of falling back to the SDK default 127.0.0.1:10000
• Soften MCP run/restart success messages to "Aspire is starting on ..." since the underlying CLI is fire-and-forget; callers should verify with get_ports or list_apphosts
• Add a get_ports MCP tool returning the full port allocation as JSON, and ignore .claude/worktrees for local worktree management

Checklist

• I have added tests, or done manual regression tests
• I have updated the documentation, if necessary

[linear]

PP-1144 Make APP_PORT configurable via global variable with derived port offsets

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
1 Accepted issue

Measures
0 Security Hotspots
3.0% Coverage on New Code
1.4% Duplication on New Code

See analysis details on SonarQube Cloud