Inspector: pause, breakpoints, stepping, scripts, and exception control

Parent: #139

Implement execution control on top of the versioned inspector session transport.

Acceptance:

• Preserve statement/source locations and publish scriptParsed events with stable script IDs.
• Implement debugger-statement and explicit pause/resume.
• Implement URL/script breakpoints, removal, and deterministic resolution events.
• Implement stepInto, stepOver, and stepOut across calls and exceptions.
• Implement pause-on-exception modes and exception events.
• Keep tree-walker and baseline/native tiers coherent, deopting or using shared hooks where required.
• Add end-to-end protocol transcripts with no silently accepted commands.

Completed implementation:

• 98c9dbb retains exact statement locations, stable scripts, debugger-statement and requested pause/resume, with tree-walker deoptimization for scripts and ordinary synchronous functions.
• eb69127 adds source retrieval, future/present URL and script-ID breakpoints, deterministic nearest-statement resolution, repeated hits, and removal.
• 6344e53 implements logical-depth stepInto/stepOver/stepOut across calls and caught exceptions.
• 357f01d implements none/all/uncaught exception policy with origin/fallback detection, exceptionThrown events, adjusted locations, and no duplicate caught/uncaught notifications.
• 835831d adds instruction-indexed debugger checkpoints to suspendable generator/async VM chunks across yield/await, disables checkpoint-skipping quick paths in debug chunks, covers VM throws, and publishes the machine-readable 16-command/8-event inventory with deterministic -32601 behavior.

Verification:

• zig build test -Dtest-filter='C-API: debugger checkpoints survive generator yield and async await' — 2/2, no leaks.
• zig build test -Dtest-filter='C-API: inspector protocol inventory has no hidden commands' — 2/2, no leaks.
• zig build test-c-api — C and C++ hosts pass; 117/117 declarations complete and present.
• Accumulated zig build test gate — 811/811 tests passed.

Dynamic eval/module/function-constructor script discovery is explicitly tracked in #155; paused frames, scopes, and remote values remain in #154.

Completed and pushed to main through 835831d. All acceptance criteria and documented verification gates are green; remaining inspector expansion is tracked by #154 and #155.