Extract GlobalConfig store from WorktreeApi.fs

[0101]

Problem

src/Server/WorktreeApi.fs was the largest production module (870 lines) and mixed four concerns: machine-level config persistence, DashboardResponse projection, worktree actions, and IWorktreeApi wiring. Roughly 250 of those lines were the machine-level ~/.treemon/config.json read/modify/write store — and that concern already had its own test suites (ConfigWriterTests.fs, WorktreeRootsConfigTests.fs), so the boundary existed; the code just lived in the wrong module.

This is candidate #7 from the code-improvement survey on this branch (the same view/state extraction lens that drove the earlier App.fs work).

Changes

Behavior-preserving extraction — no config format, key semantics, locking, atomic-write, or IWorktreeApi response changes.

• New src/Server/GlobalConfig.fs (263 L, module Server.GlobalConfig) — owns config.json: the single-serialized-writer lock + atomic temp-file-then-replace (updateConfigAtPath), the missing-vs-empty worktreeRoots semantics the startup resolver depends on, and the typed accessors (watched roots, canvas pane open/position, collapsed repos, last-viewed hashes, editor command/name). Module-private helpers stay private; the externally-consumed surface is internal.
• src/Server/WorktreeApi.fs 870 → 605 lines — left with just IWorktreeApi wiring + DashboardResponse assembly, calling the moved functions via open Server.GlobalConfig.
• src/Server/Server.fsproj — GlobalConfig.fs compiles before WorktreeApi.fs.
• Consumers retargeted in one atomic change (no compat shims): Program.fs (startup roots resolver) and the test files ConfigWriterTests.fs, WorktreeRootsConfigTests.fs, ServerStartupResolutionTests.fs, SmokeTests.fs.
• Hardening (from focused review): updateConfigAtPath skips directory creation when the config path has no parent dir, rather than attempting-and-catching.
• Docs kept honest: worktree-monitor.md gains a Configuration Store subsection + a GlobalConfig vs TreemonConfig decision and an updated Key Files table; code-improvements.md records the survey findings and moves Parallel startup burst + fix branch event key mismatch #7 to Done.

Tests

Full suite green on the final commit (independently re-run by the verification reviewer):

• Build: 0 errors / 0 warnings
• Unit: 845 / 845
• Fast: 959 / 959
• E2E: 342 / 342 (1 pre-existing data-conditional skip, orthogonal to this change)
• Structural: GlobalConfig.fs holds the moved symbols; the moved definitions are gone from WorktreeApi.fs (proving a move, not a copy); line count dropped ~265.

A focused-review quality gate ran over the branch diff (19 rules + 3 concern models) — 2 actionable findings, both fixed in this PR; the rest were verbatim-move/pre-existing false-positives.

[Copilot]

Pull request overview

This PR extracts the machine-level configuration store (~/.treemon/config.json read/modify/write) out of the oversized WorktreeApi.fs into a new dedicated src/Server/GlobalConfig.fs module. It is a behavior-preserving refactor — the config format, locking, atomic-write semantics, missing-vs-empty worktreeRoots distinction, and IWorktreeApi responses are unchanged. It fits the codebase's ongoing "view/state extraction" effort (candidate #7 from the code-improvement survey) by separating config persistence from IWorktreeApi wiring and DashboardResponse assembly.

Changes:

• New GlobalConfig.fs owning config.json (single-writer lock, atomic temp-file replace, typed accessors); moved symbols widened from private to internal so cross-module call sites resolve.
• WorktreeApi.fs slimmed (~870 → 605 lines) to API wiring + DashboardResponse, now open Server.GlobalConfig; Server.fsproj compiles GlobalConfig.fs before WorktreeApi.fs.
• Consumers retargeted with no compat shims: Program.fs plus tests (ConfigWriterTests, WorktreeRootsConfigTests, ServerStartupResolutionTests, SmokeTests); a small updateConfigAtPath hardening (skip dir creation when the path has no parent); docs updated.

Show a summary per file

File	Description
src/Server/GlobalConfig.fs	New module owning config.json; moved accessors/writers, now internal; adds empty-dir guard in updateConfigAtPath
src/Server/WorktreeApi.fs	Removes the config block, adds open Server.GlobalConfig; call sites use unqualified moved functions
src/Server/Server.fsproj	Adds GlobalConfig.fs to compile order before WorktreeApi.fs
src/Server/Program.fs	Retargets globalConfigDir/tryReadWorktreeRootsConfig/writeWorktreeRoots to GlobalConfig
src/Tests/ConfigWriterTests.fs	open switched to Server.GlobalConfig
src/Tests/WorktreeRootsConfigTests.fs	open switched to Server.GlobalConfig
src/Tests/ServerStartupResolutionTests.fs	Qualified refs switched to Server.GlobalConfig
src/Tests/SmokeTests.fs	Comment updated to reference GlobalConfig.globalConfigDir
docs/spec/worktree-monitor.md	Adds Configuration Store section, Key Files rows, and GlobalConfig vs TreemonConfig decision
docs/spec/future/code-improvements.md	Records survey findings; moves #7 to Done (one inaccurate line count)

Review details

• Files reviewed: 10/10 changed files
• Comments generated: 1
• Review effort level: Medium