docs: record M5.5 diagnostic findings and deferred candidate check

[kun002]

Scope

Record the final M5.5 session diagnostics in the host verification doc:

• the candidate-commit observation was deferred twice because the user moved into full-screen RDP sessions (synthetic keys could reach the remote machine)
• driver tooling must send virtual-key events; unicode text injection bypasses the IME pipeline and always yields raw text
• the TSF smoke confirms ContextIME composition/candidates/commit are healthy server-side (shurufa -> 输入法, Passed)
• VS Code typing stayed raw even with virtual keys inside a comment line; the M3 real-TSF automatic comment switch remains the unverified link
• the installer's forced reboot (SetRebootFlag on the upgrade path) is recorded as a 0.5.5 installer task: prompt instead of force, and evaluate reboot-free upgrades

Docs only; no source changes.

Verification status

Layer	Status	Evidence
real_machine_verified	partial (unchanged)	M5.5 management path installed-verified; candidate-commit observation documented with full diagnostics for the next pass