config: unify the dotbot CLI config into one file (dotbot -c config.toml)

[geonnave]

Today dotbot configuration is scattered across three overlapping surfaces -
run controller --config-path, swarm -c (actually swarmit's loader, wrapped),
and ~/.dotbot/config.toml's [fw] table - with three names for the network id
(swarm_id / network_id / swarmit_network_id) and an overloaded -c
(build-config in fw/device, config-file in swarm). This unifies the lot
into one file with a single, documented precedence chain.

The shape

One file, sections mirroring the four-namespace CLI, plus named deployments:

default_deployment = "inria"
conn     = "mqtts://broker.local:8883"   # shared; sections/deployments override
swarm_id = "0001"

[deployment.inria]                       # a deployment you SELECT, not edit
conn = "mqtts://broker.inria.fr:8883"
swarm_id = "0001"

[fw]
board = "dotbot-v3"

[run.controller]
http_port = 8000

• Precedence (one chain, no exceptions): CLI flag > env
  (DOTBOT_<SECTION>_<KEY>) > file (section > selected deployment > top-level) >
  built-in default. extra='forbid', so a typo'd key fails loud.
• Discovery: -c PATH > DOTBOT_CONFIG > nearest dotbot.toml
  (cwd-upward) > ~/.dotbot/config.toml.
• Deployment = one physical site (Inria/100, La Poste/1000), selected with
  --deployment / DOTBOT_DEPLOYMENT / default_deployment. The name was
  chosen by a four-persona review over testbed (overloads with the product
  name "the DotBot Testbed") and instance (clashes with the planned Swarm
  SDK object); deployment is clean against both and reads for the
  education/industry audience. (The simulator is not a deployment; it is
  --conn simulator.)
• MQTT credentials stay env-only (DOTBOT_MQTT_USER/PASS), never a file key.

What's in this PR

• The resolver core (dotbot/config.py): pydantic schema, discovery, deployment
  selection, one precedence function; conn validated via the existing
  parse_connection so the file and the --conn flag share one validator.
• Root dotbot -c/--config + --deployment (loads + selects into the Click
  context). fw/device --config/-c renamed to --build-config to free
  -c (clean break, no alias).
• fw/device now read their option defaults from the config (an explicit flag
  still wins; with no config, behavior is unchanged).
• Read-only management commands: dotbot config path/show and
  dotbot deployment list/show.
• A configuration reference doc page.

Deferred (own follow-ups, called out so they aren't forgotten)

• run controller consumption - it is also invoked directly by
  run simulator (no root context), and still carries --config-path + the
  conn-translation; migrating it cleanly wants care + bench validation.
• swarm consumption - dotbot swarm mounts swarmit's own CLI (its own
  -c); unifying it is a cross-repo decision, so it is intentionally untouched
  here.
• Retiring network_id / swarmit_network_id in favour of one swarm_id -
  touches the adapter layer; separate change.
• The ~/.dotbot/config.toml auto-fallback is wired but kept OFF for now
  (include_user_file=False): that file is still owned by the legacy fw
  segger_dir reader, and switches on when fw migrates onto the resolver.

Validation

343 tests pass (headless): the resolver's precedence/discovery/deployment
permutations, the root wiring, the build-config rename, the helpers. black /
isort / ruff clean; docs build clean. No runtime/hardware path is changed by
this PR - the consumers either fall back to today's defaults when no config is
present, or are deferred above.

[codecov]

Codecov Report

❌ Patch coverage is 98.11482% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.74%. Comparing base (a6f0cda) to head (11fb85e).
⚠️ Report is 193 commits behind head on develop.

Files with missing lines	Patch %	Lines
dotbot/cli/deployment_cmd.py	94.26%	9 Missing ⚠️
dotbot/cli/config_cmd.py	96.62%	3 Missing ⚠️
dotbot/cli/device.py	81.25%	3 Missing ⚠️
dotbot/cli/swarm.py	75.00%	3 Missing ⚠️
dotbot/config.py	98.03%	3 Missing ⚠️
dotbot/cli/_fw_helpers.py	93.75%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #266      +/-   ##
===========================================
+ Coverage    82.10%   83.74%   +1.64%     
===========================================
  Files          105      116      +11     
  Lines         9677    10815    +1138     
  Branches       571      569       -2     
===========================================
+ Hits          7945     9057    +1112     
- Misses        1729     1754      +25     
- Partials         3        4       +1     

Files with missing lines	Coverage Δ
dotbot/cli/_cfg.py	100.00% <100.00%> (ø)
dotbot/cli/_lazy.py	95.23% <100.00%> (+0.50%)	⬆️
dotbot/cli/_swarm_inject.py	100.00% <100.00%> (ø)
dotbot/cli/fw.py	88.80% <100.00%> (+1.20%)	⬆️
dotbot/cli/gateway.py	100.00% <100.00%> (ø)
dotbot/cli/main.py	100.00% <100.00%> (ø)
dotbot/controller_app.py	96.90% <100.00%> (+0.13%)	⬆️
dotbot/tests/test_cli_cfg_helper.py	100.00% <100.00%> (ø)
dotbot/tests/test_cli_config.py	100.00% <100.00%> (ø)
dotbot/tests/test_cli_deployment_fetch.py	100.00% <100.00%> (ø)
... and 15 more

... and 1 file with indirect coverage changes

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.

[geonnave]

Huge PR! But at least half is tests + docs. Worth it in my opinion, as it now enables much much simpler developer experience such as:

dotbot config init --conn mqtts://argus.paris.inria.fr:8883 --swarm-id 1234
dotbot swarm status
dotbot swarm flash ./artifacts/rgbled-sandbox-dotbot-v3.bin -ys
dotbot swarm stop