Start-Copilot: map --assisted-approval, --allow-all-tools, --usage-output-file, native --enable-mcp-server

[shmuelie]

Adds first-class Start-Copilot / Get-CopilotLaunchPlan parameters for Copilot CLI launch flags that previously had no mapping (only reachable via -RemainingArgs), and extends the MCP enable behavior.

Parameter	CLI flag	Notes
-AssistedApproval	--assisted-approval	Review permission requests with the assisted-approval safety judge (needs experimental mode, on by default)
-AllowAllTools	--allow-all-tools	Auto-approve tools while keeping file-path/URL verification; implies not passing --allow-all
-UsageOutputFile	--usage-output-file <path>	Write final usage statistics as JSON; most useful with -Prompt
-EnableMcpServer (existing)	--enable-mcp-server	Now also passes the CLI's native flag, so a server disabled in the Copilot settings is enabled for the run — in addition to overriding the path-based autoConnect policy

The parameters live on Get-CopilotLaunchPlan (the shared core that builds the argument vector); Start-Copilot surfaces them and auto-forwards every bound parameter the core accepts. -AllowAllTools suppresses the default --allow-all so the two are not emitted together.

Tests (6 new cases asserting the emitted args, the allow-all suppression, native enable-mcp emission, and Start-Copilot -PassThru forwarding), README, and CHANGELOG updated. Full Copilot suite: 65 passed, 0 failed; Test-Modules.ps1 green.

Closes #117
Closes #118
Closes #119
Closes #120

[shmuelie]

Peer review (Correctness, Skeptic, Craft panel). No blocking bugs — the suppression logic, no-double-emit, parameter parity, and Start-Copilot forwarding were all confirmed correct. Applied the panel's important/minor findings in the latest commit:

• -AssistedApproval + -NoExperimental (Skeptic): the CLI needs experimental mode for the judge to engage — now emits a Write-Warning, with a test.
• -AllowAllTools headless semantics (Skeptic): documented that it keeps file-path/URL verification, so fully non-interactive -Prompt use may also need -AllowAllPaths/-AllowAllUrls.
• -EnableMcpServer behavior change (Skeptic/Correctness): documented that the native --enable-mcp-server is a no-op for an already-enabled server, and added a test with an mcp-config.json present asserting the named server is enabled (native flag) and not disabled.
• Test coverage (all three): added -NoAllowAll -AllowAllTools suppression, --usage-output-file value-adjacency in the passthrough test, and an -EnableMcpServer passthrough test.
• README (Skeptic): refreshed the "sensible defaults" bullet to note the -AllowAllTools middle ground and list the new flags.

Copilot suite now 69 passed, 0 failed; Test-Modules.ps1 green.