[Bugfix #451] Replace intrusive reconnect overlay with status dot + fix premature give-up

[waleedkadous]

Summary

Fixes two issues with the terminal reconnect feature (PR #445):

1. UX: Replaced the yellow "Reconnecting..." overlay (which covered terminal content) with a small status dot indicator in the terminal controls area
2. Bug: Fixed premature reconnect give-up caused by a flawed rapid failure detection mechanism

Fixes #451

Root Cause

UX issue: The terminal-reconnecting-overlay div was positioned absolutely over the terminal content, obscuring output during reconnection attempts.

Premature give-up: The rapidFailures counter counted WebSocket connections that closed within 2 seconds of creation. When the server was temporarily unreachable, each failed connection attempt (which fails in <2s by definition) was counted as a "rapid failure" — regardless of the backoff delay between attempts. After just 5 such failures (~15 seconds), the reconnect permanently gave up, even though the session was still alive on the server (page reload would succeed).

Fix

1. Status dot: Added a small colored dot to the TerminalControls component:

   • No dot when connected (clean state)
   • Yellow pulsing dot when reconnecting
   • Red dot when disconnected

2. Reconnect logic: Removed the flawed rapidFailures mechanism entirely. Increased MAX_ATTEMPTS from 15 to 50 (with 30s backoff cap, gives ~20 minutes of retry). Exponential backoff alone is sufficient for graceful degradation.

Test Plan

• Regression test added (verifies 10+ rapid failures don't cause premature give-up)
• Status dot tests (reconnecting dot shown/hidden, disconnected dot after max attempts)
• Build passes
• All reconnect tests pass (11/11)
• All backend tests pass (1798/1798)
• Pre-existing failures in fit-scroll and ime-dedup tests confirmed on main