fix: harden workspace boundaries and bound architecture analysis

[linnnn89]

Changes

Harden workspace execution and disk boundaries, and make architecture discovery bounded and cancellable. Repository-local git.cmd and executable fsmonitor settings no longer run through Git probes; linked worktrees are recognized and failed status checks remain unknown. Git probes require 2.36 or later.

Cache/trash paths reject existing links and junctions, cache mutations verify directory identity, and cleanup preserves legacy/unrecognized files. Architecture discovery rejects outside project descriptors and limits entries, descriptor bytes, project count and actual formatted MCP output. The C# whitespace counterexample no longer blocks declaration parsing. Partial trash outcomes and existing workspace recovery remain intact.

Validation

• Local Windows x64 / Node 24.19.0: npm run check, 385/385 passed, including 12 new safety regressions, build, stdio and delivery verification.
• Real Roslyn MCP: 22 scenarios passed, including warm identity and MSBuild cancellation/crash/timeout cleanup.
• Error/recovery contracts: 16 scenarios passed.
• Formatted-output regression: 137 project declarations previously returned 32,847 characters; now 32,238 within the 32,768 limit.
• Delivery verification matched; Markdown/link and diff checks passed.

Remaining boundaries

No atomic sandbox against concurrent path replacement, no forced interruption guarantee for permanently stalled OS I/O, and no permanent overflow attachment lease. Fixed-project connections (N1), bounded admission (N3), production cleanup identity (A9), and remaining consumer/long-running validation stay on the roadmap. Desktop tests and existing Codex connections were not refreshed in this change. Required CI must pass for this PR head before merge.