Epic: Permissions Improvements

## Description

When the CLI was shipped for public preview, it shipped with a _passable_, but sometimes incorrect, often overbearing, and lacking in configuration, experience.

## Public Issues

These are the issues that I could find relating to permissions in this repo. I intend to go through these and break them apart into themes.

- [x] https://github.com/github/copilot-cli/issues/67
- On Windows, built-in `findstr` uses args like `/i`
- On PowerShell, built-in `-replace` syntax accepts regexes
- [ ] https://github.com/github/copilot-cli/issues/144
- Either expand variables when `$HOME` (etc) is passed to `/add-dir`, or reject args that aren't dirs that exist
- [x] https://github.com/github/copilot-cli/issues/145
- Asking for an alias to `--allow-all-tools --allow-all-paths`
- [x] https://github.com/github/copilot-cli/issues/159
- With heredoc syntax (`cat << 'EOF' (some content) 'EOF'`), we look for paths inside `(some content)` but should not
- Awk command parsing misses cases `awk '/^ir:/,/^sentinels:/{print NR": "$0}' xyz.yml | head -220` and `cd /workdir && awk '/CreateTable/,/name:/'
Services/Migrations/20251001031252_InitialCreate.cs`
- [ ] https://github.com/github/copilot-cli/issues/162 (I think)
- Asking for a permissions display/editor
- [x] https://github.com/github/copilot-cli/issues/176
- Another one about PowerShell `-replace` syntax
- [ ] https://github.com/github/copilot-cli/issues/179
- Asking for more flexibility about global config defaults
- [x] https://github.com/github/copilot-cli/issues/211
- `2>&1` detected as path (already fixed?) and should allow redirection `> /dev/null`
- [x] https://github.com/github/copilot-cli/issues/216
- Should know that `gh api /repos/myuser/myrepo` refers to parts of a URL, not a file path
- [x] https://github.com/github/copilot-cli/issues/219
- PowerShell `Select-String -Pattern (regex?)` and `'string' -match (regex)` syntax
- [x] https://github.com/github/copilot-cli/issues/247
- Should know that `bazel test //foo/bar:baz` resolves `foo/bar` within the Bazel workspace
- But I'm not sure we should be baking in knowledge of how Bazel locates its workspace root
- Also, even if you approve it, it keeps asking. We should fix that part at least.
- [x] https://github.com/github/copilot-cli/issues/261
- When running under Cygwin, paths become weird (`/c:/Users/etc`) and we don't understand them
- Not sure we should fix Cygwin-specific things unless we get more reports
- [ ] https://github.com/github/copilot-cli/issues/285
- Asking for more granular control over the file write tool (so it would do *more* permission requests)
- [ ] https://github.com/github/copilot-cli/issues/291
- Asking for shell permissions requests to contain an LLM-generated explanation of what the call would do
- Not just repeating the intent we already get, but rather explaining what all the flags mean etc.
- [x] https://github.com/github/copilot-cli/issues/301
- Very small tweak to phrasing in file write confirmation prompt
- [x] https://github.com/github/copilot-cli/issues/306
- [x] https://github.com/github/copilot-cli/issues/307
- Meta-issue (AI generated?) summarizing many of the other ones here
- [x] https://github.com/github/copilot-cli/issues/342
- Draft PR: https://github.com/github/sweagentd/pull/7608
- [ ] PowerShell `Measure-Object` should be approved by default

## Other things to think about

- when a user opts to approve a command for the rest of the session we could persist that into the session log such that when they later `--resume` they don't have to go through all the same approvals again