fix(git): run post-checkout hook after worktree creation bootstrap (#2721)

Worktrees are created with `git worktree add --no-checkout` and populated
with `git reset --hard`, neither of which runs git's post-checkout hook.
Invoke the hook explicitly after population with git's standard arguments
(null ref previous HEAD, checked-out HEAD, flag 1) and the worktree as cwd,
mirroring `git worktree add` without --no-checkout.

A missing or non-executable hook is skipped (matching git) and a failing
hook is logged as a warning, never failing worktree creation or session
bootstrap. Applied to both the web server git service and the VS Code
runtime's git service.

packages/web/server/lib/git/DOCUMENTATION.md

@@ -48,7 +48,7 @@ The following functions are exported and used by the web server:
 ### Worktree Operations
 - `getWorktrees(directory)`: List all git worktrees for a repository.
 - `validateWorktreeCreate(directory, input)`: Validate worktree creation parameters (mode, branchName, startRef, upstream config).
-- `createWorktree(directory, input)`: Create a new worktree (supports 'new' and 'existing' modes, upstream setup).
+- `createWorktree(directory, input)`: Create a new worktree (supports 'new' and 'existing' modes, upstream setup). After populating the worktree, the repository's `post-checkout` hook runs once with git's standard arguments (null ref as previous HEAD, the checked-out HEAD, and flag `1`) from the worktree directory, mirroring `git worktree add` without `--no-checkout`; a missing or non-executable hook is skipped and a failing hook is logged as a warning, never failing worktree creation or the session bootstrap.
 - `removeWorktree(directory, input)`: Remove a worktree (optionally delete local branch).
 - `isLinkedWorktree(directory)`: Check if directory is a linked worktree (not primary).
 
@@ -95,6 +95,7 @@ The following functions are internal helpers used by exported functions:
 - `resolveCandidateDirectory(...)`: Generate unique worktree directory candidates.
 - `resolveBranchForExistingMode(...)`: Resolve branch for existing-mode worktree creation.
 - `applyUpstreamConfiguration(...)`: Set upstream tracking for new branches.
+- `runPostCheckoutHook(directory)`: Invoke the worktree's `post-checkout` hook after population, because `git worktree add --no-checkout` and the bootstrap's `git reset --hard` never run git hooks. Runs with git's standard arguments and the worktree as cwd; skips missing/non-executable hooks and never throws on hook failure.
 - And various other internal helpers for Git command execution and parsing.
 
 ## Response Contracts