fix(insights): count read-shaped shell commands as reads, not as verification

[iamtoruk]

Fixes #941.

Two detectors treated the same Bash call inconsistently: READ_TOOL_NAMES ignored shell reads entirely (a session searching with rg read nothing as far as read-edit-ratio was concerned), while countRetries treated every Bash call as a verification step (edit -> grep -> edit scored as rework). Both feed the Optimize tab and the health grade, so bash-first workflows scored worse the more disciplined they were about looking before editing.

One shared classifier fixes both sides: isReadShapedBashCommand (bash-utils) accepts a command only when every segment (split on &&, ;, |) is a read-only inspection command - rg/grep/cat/head/ls/find/wc/jq and friends, plus git subcommands that cannot mutate under any flag (log, diff, status, show, blame, grep, shortlog, describe, rev-parse, ls-files). Unknown or mixed commands stay non-read, the conservative default both call sites want.

• detectLowReadEditRatio now counts read-shaped bash calls as reads; compactOptimizeInput retains the (capped) command for bash tool_use blocks so the detector can classify them.
• countRetries no longer takes a read-shaped shell step as verification; a command-less bash step keeps the old behavior.
• No cache bump needed: classification runs at serve time from cached turns (cachedTurnToClassified), so the corrected retry counts apply to existing caches immediately.

Measured on a real 7-day corpus (3,928 sessions): 1,053 previously-invisible shell reads (ratio 1.70:1 -> 2.01:1 against the 4:1 threshold) and 14 phantom retries removed (770 -> 756). The issue reporter's rg-first corpus shows a much larger swing (0.34:1 -> 3.72:1); this corpus is echo/git/python3-heavy, so the honest effect here is smaller but directionally identical.

Tests: read-shaped-bash ratio positive/negative in tests/optimize.test.ts, retry positive/negative/unknown-conservative in tests/classifier.test.ts, and the command classifier's accept/reject/quoting matrix in tests/bash-commands.test.ts. tsc clean; 147 tests green across the three suites.